size some stringbuffer to prevent re-alloc

found by the simple expidient of putting asserts in
the resize routine. Where an explicit const size is used,
I started with 32 and kept doubling until that site
did not need resizing anymore.

Change-Id: I998787edc940d0a3ba23b5ac37131ab9ecd300f4
Reviewed-on: https://gerrit.libreoffice.org/81138
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

43 files changed, 131 insertions, 128 deletions

diff --git a/codemaker/source/cppumaker/cpputype.cxx b/codemaker/source/cppumaker/cpputype.cxx
index 67b842f0c3d1..a16256d4c353 100644
--- a/codemaker/source/cppumaker/cpputype.cxx
+++ b/codemaker/source/cppumaker/cpputype.cxx
@@ -1004,7 +1004,7 @@ OUString CppuType::resolveAllTypedefs(OUString const & name) const
             u2b(dynamic_cast<unoidl::TypedefEntity&>(*ent).getType()), &k2));
         k1 += k2; //TODO: overflow
     }
-    OUStringBuffer b;
+    OUStringBuffer b(k1*2 + n.getLength());
     for (sal_Int32 i = 0; i != k1; ++i) {
         b.append("[]");
     }
@@ -2675,7 +2675,7 @@ OUString typeToIdentifier(OUString const & name)
 {
     sal_Int32 k;
     OUString n(b2u(codemaker::UnoType::decompose(u2b(name), &k)));
-    OUStringBuffer b;
+    OUStringBuffer b(4*k + n.getLength());
     for (sal_Int32 i = 0; i != k; ++i) {
         b.append("seq_");
     }
@@ -3587,7 +3587,7 @@ void ServiceType::dumpHppFile(
                 for (const unoidl::SingleInterfaceBasedServiceEntity::Constructor::Parameter& param :
                      cons.parameters) {
                     o << ", ";
-                    OUStringBuffer buf;
+                    OUStringBuffer buf(2 + param.type.getLength());
                     if (param.rest) {
                         buf.append("[]");
                     }
diff --git a/configmgr/source/childaccess.cxx b/configmgr/source/childaccess.cxx
index 82ca003c1703..68bc0b01351c 100644
--- a/configmgr/source/childaccess.cxx
+++ b/configmgr/source/childaccess.cxx
@@ -104,7 +104,7 @@ std::vector<OUString> ChildAccess::getRelativePath() {
 }
 
 OUString ChildAccess::getRelativePathRepresentation() {
-    OUStringBuffer path;
+    OUStringBuffer path(128);
     rtl::Reference< Access > parent(getParentAccess());
     if (parent.is()) {
         path.append(parent->getRelativePathRepresentation());
diff --git a/configmgr/source/data.cxx b/configmgr/source/data.cxx
index 7ff344650ebc..4f91d3b25612 100644
--- a/configmgr/source/data.cxx
+++ b/configmgr/source/data.cxx
@@ -49,7 +49,7 @@ bool decode(
     assert(
         begin >= 0 && begin <= end && end <= encoded.getLength() &&
         decoded != nullptr);
-    OUStringBuffer buf;
+    OUStringBuffer buf(end - begin);
     while (begin != end) {
         sal_Unicode c = encoded[begin++];
         if (c == '&') {
@@ -82,7 +82,8 @@ OUString Data::createSegment(
     if (templateName.isEmpty()) {
         return name;
     }
-    OUStringBuffer buf(templateName);
+    OUStringBuffer buf(128);
+    buf.append(templateName);
         //TODO: verify template name contains no bad chars?
     buf.append("['");
     for (sal_Int32 i = 0; i < name.getLength(); ++i) {
@@ -207,7 +208,7 @@ rtl::Reference< Node > Data::resolvePathRepresentation(
     }
     NodeMap const & components = getComponents();
     NodeMap::const_iterator i(components.find(seg));
-    OUStringBuffer canonic;
+    OUStringBuffer canonic(128);
     rtl::Reference< Node > parent;
     int finalized = NO_LAYER;
     for (rtl::Reference< Node > p(i == components.end() ? nullptr : i->second);;) {
diff --git a/configmgr/source/xcsparser.cxx b/configmgr/source/xcsparser.cxx
index 24e1dc008312..c0b34974157b 100644
--- a/configmgr/source/xcsparser.cxx
+++ b/configmgr/source/xcsparser.cxx
@@ -321,7 +321,7 @@ void XcsParser::characters(xmlreader::Span const & text) {
 
 void XcsParser::handleComponentSchema(xmlreader::XmlReader & reader) {
     //TODO: oor:version, xml:lang attributes
-    OStringBuffer buf;
+    OStringBuffer buf(256);
     buf.append('.');
     bool hasPackage = false;
     bool hasName = false;
diff --git a/configmgr/source/xcuparser.cxx b/configmgr/source/xcuparser.cxx
index 89508be97992..03e3c60ab067 100644
--- a/configmgr/source/xcuparser.cxx
+++ b/configmgr/source/xcuparser.cxx
@@ -220,7 +220,7 @@ XcuParser::Operation XcuParser::parseOperation(xmlreader::Span const & text) {
 }
 
 void XcuParser::handleComponentData(xmlreader::XmlReader & reader) {
-    OStringBuffer buf;
+    OStringBuffer buf(256);
     buf.append('.');
     bool hasPackage = false;
     bool hasName = false;
diff --git a/desktop/source/deployment/misc/dp_misc.cxx b/desktop/source/deployment/misc/dp_misc.cxx
index a23855109c36..7b4aafb3b083 100644
--- a/desktop/source/deployment/misc/dp_misc.cxx
+++ b/desktop/source/deployment/misc/dp_misc.cxx
@@ -243,7 +243,7 @@ namespace {
 OUString encodeForRcFile( OUString const & str )
 {
     // escape $\{} (=> rtl bootstrap files)
-    OUStringBuffer buf;
+    OUStringBuffer buf(64);
     sal_Int32 pos = 0;
     const sal_Int32 len = str.getLength();
     for ( ; pos < len; ++pos ) {
@@ -265,7 +265,7 @@ OUString encodeForRcFile( OUString const & str )
 
 OUString makeURL( OUString const & baseURL, OUString const & relPath_ )
 {
-    OUStringBuffer buf;
+    OUStringBuffer buf(128);
     if (baseURL.getLength() > 1 && baseURL[ baseURL.getLength() - 1 ] == '/')
         buf.append( std::u16string_view(baseURL).substr(0, baseURL.getLength() - 1) );
     else
diff --git a/framework/source/accelerators/storageholder.cxx b/framework/source/accelerators/storageholder.cxx
index 567c7af65220..d12a13fbc47a 100644
--- a/framework/source/accelerators/storageholder.cxx
+++ b/framework/source/accelerators/storageholder.cxx
@@ -354,7 +354,7 @@ css::uno::Reference< css::embed::XStorage > StorageHolder::getParentStorage(cons
             return m_xRoot;
 
         // c)
-        OUStringBuffer sParentPath;
+        OUStringBuffer sParentPath(64);
         sal_Int32       i = 0;
         for (i = 0; i < c - 1; ++i)
         {
diff --git a/framework/source/fwi/classes/protocolhandlercache.cxx b/framework/source/fwi/classes/protocolhandlercache.cxx
index 8a27747bcb48..40e938e04c32 100644
--- a/framework/source/fwi/classes/protocolhandlercache.cxx
+++ b/framework/source/fwi/classes/protocolhandlercache.cxx
@@ -200,13 +200,13 @@ void HandlerCFGAccess::read( HandlerHash& rHandlerHash, PatternHash& rPatternHas
     sal_Int32 nTarget=0;
     for( nSource=0; nSource<nSourceCount; ++nSource )
     {
-        OUStringBuffer sPath( SETNAME_HANDLER );
-        sPath.append(CFG_PATH_SEPARATOR);
-        sPath.append(lNames[nSource]);
-        sPath.append(CFG_PATH_SEPARATOR);
-        sPath.append(PROPERTY_PROTOCOLS);
+        lFullNames[nTarget] =
+            SETNAME_HANDLER
+            CFG_PATH_SEPARATOR +
+            lNames[nSource] +
+            CFG_PATH_SEPARATOR
+            PROPERTY_PROTOCOLS;
 
-        lFullNames[nTarget]  = sPath.makeStringAndClear();
         ++nTarget;
     }
 
diff --git a/framework/source/services/substitutepathvars.cxx b/framework/source/services/substitutepathvars.cxx
index 97c91ea9f9d3..3c5733d47a1b 100644
--- a/framework/source/services/substitutepathvars.cxx
+++ b/framework/source/services/substitutepathvars.cxx
@@ -286,7 +286,7 @@ OUString SubstitutePathVariables::GetPathVariableValue() const
 
     if ( pEnv )
     {
-        const int PATH_EXTEND_FACTOR = 120;
+        const int PATH_EXTEND_FACTOR = 200;
         OUString       aTmp;
         OUString       aPathList( pEnv, strlen( pEnv ), osl_getThreadTextEncoding() );
         OUStringBuffer aPathStrBuffer( aPathList.getLength() * PATH_EXTEND_FACTOR / 100 );
diff --git a/framework/source/services/urltransformer.cxx b/framework/source/services/urltransformer.cxx
index ce9ae752ec60..23a314026588 100644
--- a/framework/source/services/urltransformer.cxx
+++ b/framework/source/services/urltransformer.cxx
@@ -76,7 +76,7 @@ void lcl_ParserHelper(INetURLObject& _rParser, css::util::URL& _rURL,bool _bUseI
         // Don't add last segment as it is the name!
         --nCount;
 
-        OUStringBuffer aPath;
+        OUStringBuffer aPath(128);
         for ( sal_Int32 nIndex = 0; nIndex < nCount; nIndex++ )
         {
             aPath.append( '/');
diff --git a/framework/source/uiconfiguration/moduleuiconfigurationmanager.cxx b/framework/source/uiconfiguration/moduleuiconfigurationmanager.cxx
index 36631222539e..691c4b69a794 100644
--- a/framework/source/uiconfiguration/moduleuiconfigurationmanager.cxx
+++ b/framework/source/uiconfiguration/moduleuiconfigurationmanager.cxx
@@ -222,7 +222,7 @@ private:
 
 // important: The order and position of the elements must match the constant
 // definition of "css::ui::UIElementType"
-static const char* UIELEMENTTYPENAMES[] =
+static OUStringLiteral UIELEMENTTYPENAMES[] =
 {
     "",  // Dummy value for unknown!
     UIELEMENTTYPE_MENUBAR_NAME,
@@ -250,7 +250,7 @@ sal_Int16 RetrieveTypeFromResourceURL( const OUString& aResourceURL )
             OUString aTypeStr( aTmpStr.copy( 0, nIndex ));
             for ( int i = 0; i < ui::UIElementType::COUNT; i++ )
             {
-                if ( aTypeStr.equalsAscii( UIELEMENTTYPENAMES[i] ))
+                if ( aTypeStr == UIELEMENTTYPENAMES[i] )
                     return sal_Int16( i );
             }
         }
@@ -358,11 +358,10 @@ void ModuleUIConfigurationManager::impl_preloadUIElementTypeList( Layer eLayer,
         Reference< XStorage > xElementTypeStorage = rElementTypeData.xStorage;
         if ( xElementTypeStorage.is() )
         {
-            OUStringBuffer aBuf( RESOURCEURL_PREFIX_SIZE );
-            aBuf.append( RESOURCEURL_PREFIX );
-            aBuf.appendAscii( UIELEMENTTYPENAMES[ nElementType ] );
-            aBuf.append( "/" );
-            OUString aResURLPrefix( aBuf.makeStringAndClear() );
+            OUString aResURLPrefix =
+                RESOURCEURL_PREFIX +
+                UIELEMENTTYPENAMES[ nElementType ] +
+                "/";
 
             UIElementDataHashMap& rHashMap = rElementTypeData.aElementsHashMap;
             Sequence< OUString > aUIElementNames = xElementTypeStorage->getElementNames();
@@ -808,7 +807,7 @@ void ModuleUIConfigurationManager::impl_Initialize()
             Reference< XStorage > xElementTypeStorage;
             try
             {
-                const OUString sName( OUString::createFromAscii( UIELEMENTTYPENAMES[i] ) );
+                const OUString sName( UIELEMENTTYPENAMES[i] );
                 if( xNameAccess->hasByName( sName ) )
                     xNameAccess->getByName( sName ) >>= xElementTypeStorage;
             }
@@ -1583,7 +1582,7 @@ void SAL_CALL ModuleUIConfigurationManager::storeToStorage( const Reference< XSt
             try
             {
                 Reference< XStorage > xElementTypeStorage( Storage->openStorageElement(
-                                                            OUString::createFromAscii( UIELEMENTTYPENAMES[i] ), ElementModes::READWRITE ));
+                                                              UIELEMENTTYPENAMES[i], ElementModes::READWRITE ));
                 UIElementType&        rElementType = m_aUIElements[LAYER_USERDEFINED][i];
 
                 if ( rElementType.bModified && xElementTypeStorage.is() )
diff --git a/framework/source/uiconfiguration/uiconfigurationmanager.cxx b/framework/source/uiconfiguration/uiconfigurationmanager.cxx
index 9f309f7d7656..778028f98d42 100644
--- a/framework/source/uiconfiguration/uiconfigurationmanager.cxx
+++ b/framework/source/uiconfiguration/uiconfigurationmanager.cxx
@@ -197,7 +197,7 @@ private:
 
 // important: The order and position of the elements must match the constant
 // definition of "css::ui::UIElementType"
-static const char* UIELEMENTTYPENAMES[] =
+static OUStringLiteral UIELEMENTTYPENAMES[] =
 {
     "",  // Dummy value for unknown!
     UIELEMENTTYPE_MENUBAR_NAME,
@@ -225,7 +225,7 @@ sal_Int16 RetrieveTypeFromResourceURL( const OUString& aResourceURL )
             OUString aTypeStr( aTmpStr.copy( 0, nIndex ));
             for ( int i = 0; i < UIElementType::COUNT; i++ )
             {
-                if ( aTypeStr.equalsAscii( UIELEMENTTYPENAMES[i] ))
+                if ( aTypeStr == UIELEMENTTYPENAMES[i] )
                     return sal_Int16( i );
             }
         }
@@ -283,11 +283,10 @@ void UIConfigurationManager::impl_preloadUIElementTypeList( sal_Int16 nElementTy
         Reference< XStorage > xElementTypeStorage = rElementTypeData.xStorage;
         if ( xElementTypeStorage.is() )
         {
-            OUStringBuffer aBuf( RESOURCEURL_PREFIX_SIZE );
-            aBuf.append( RESOURCEURL_PREFIX );
-            aBuf.appendAscii( UIELEMENTTYPENAMES[ nElementType ] );
-            aBuf.append( "/" );
-            OUString aResURLPrefix( aBuf.makeStringAndClear() );
+            OUString aResURLPrefix =
+                RESOURCEURL_PREFIX +
+                UIELEMENTTYPENAMES[ nElementType ] +
+                "/";
 
             UIElementDataHashMap& rHashMap = rElementTypeData.aElementsHashMap;
             Sequence< OUString > aUIElementNames = xElementTypeStorage->getElementNames();
@@ -637,7 +636,7 @@ void UIConfigurationManager::impl_Initialize()
             Reference< XStorage > xElementTypeStorage;
             try
             {
-                xElementTypeStorage = m_xDocConfigStorage->openStorageElement( OUString::createFromAscii( UIELEMENTTYPENAMES[i] ), nModes );
+                xElementTypeStorage = m_xDocConfigStorage->openStorageElement( UIELEMENTTYPENAMES[i], nModes );
             }
             catch ( const css::container::NoSuchElementException& )
             {
@@ -1308,7 +1307,7 @@ void SAL_CALL UIConfigurationManager::storeToStorage( const Reference< XStorage
             try
             {
                 Reference< XStorage > xElementTypeStorage( Storage->openStorageElement(
-                                                           OUString::createFromAscii( UIELEMENTTYPENAMES[i] ), ElementModes::READWRITE ));
+                                                            UIELEMENTTYPENAMES[i], ElementModes::READWRITE ));
                 UIElementType& rElementType = m_aUIElements[i];
 
                 if ( rElementType.bModified && xElementTypeStorage.is() )
diff --git a/i18npool/source/localedata/localedata.cxx b/i18npool/source/localedata/localedata.cxx
index 68a0d9359b47..e379b403248c 100644
--- a/i18npool/source/localedata/localedata.cxx
+++ b/i18npool/source/localedata/localedata.cxx
@@ -538,8 +538,6 @@ oslGenericFunction lcl_LookupTableHelper::getFunctionSymbolByName(
                 (bFallback && aFallback.equalsAscii(i.pLocale)))
         {
 #ifndef DISABLE_DYNLOADING
-            OUStringBuffer aBuf(sal::static_int_cast<int>(
-                        strlen(i.pLocale) + 1 + strlen(pFunction)));
             {
                 ::osl::MutexGuard aGuard( maMutex );
                 for (LocaleDataLookupTableItem & rCurrent : maLookupTable)
@@ -551,9 +549,10 @@ oslGenericFunction lcl_LookupTableHelper::getFunctionSymbolByName(
                         {
                             (*pOutCachedItem).reset(new LocaleDataLookupTableItem( rCurrent ));
                             (*pOutCachedItem)->localeName = i.pLocale;
+                            OString sSymbolName = rtl::OStringView(pFunction) + "_" +
+                                    (*pOutCachedItem)->localeName;
                             return (*pOutCachedItem)->module->getFunctionSymbol(
-                                    aBuf.appendAscii( pFunction).append( cUnder).
-                                    appendAscii( (*pOutCachedItem)->localeName).makeStringAndClear());
+                                    sSymbolName.getStr());
                         }
                         else
                             return nullptr;
@@ -562,14 +561,14 @@ oslGenericFunction lcl_LookupTableHelper::getFunctionSymbolByName(
             }
             // Library not loaded, load it and add it to the list.
 #ifdef SAL_DLLPREFIX
-            aBuf.ensureCapacity(strlen(i.pLib) + 6);    // mostly "lib*.so"
-            aBuf.append( SAL_DLLPREFIX ).appendAscii(i.pLib).append( SAL_DLLEXTENSION );
+            OString sModuleName =    // mostly "lib*.so"
+                SAL_DLLPREFIX + rtl::OStringView(i.pLib) + SAL_DLLEXTENSION;
 #else
-            aBuf.ensureCapacity(strlen(i.pLib) + 4);    // mostly "*.dll"
-            aBuf.appendAscii(i.pLib).append( SAL_DLLEXTENSION );
+            OString sModuleName =    // mostly "*.dll"
+                rtl::OStringView(i.pLib) + SAL_DLLEXTENSION;
 #endif
             std::unique_ptr<osl::Module> module(new osl::Module());
-            if ( module->loadRelative(&thisModule, aBuf.makeStringAndClear()) )
+            if ( module->loadRelative(&thisModule, sModuleName.getStr()) )
             {
                 ::osl::MutexGuard aGuard( maMutex );
                 auto pTmpModule = module.get();
@@ -578,9 +577,8 @@ oslGenericFunction lcl_LookupTableHelper::getFunctionSymbolByName(
                 if( pOutCachedItem )
                 {
                     pOutCachedItem->reset(new LocaleDataLookupTableItem( maLookupTable.back() ));
-                    return pTmpModule->getFunctionSymbol(
-                            aBuf.appendAscii(pFunction).append(cUnder).
-                            appendAscii((*pOutCachedItem)->localeName).makeStringAndClear());
+                    OString sSymbolName = rtl::OStringView(pFunction) + "_" + (*pOutCachedItem)->localeName;
+                    return pTmpModule->getFunctionSymbol(sSymbolName.getStr());
                 }
                 else
                     return nullptr;
@@ -1444,12 +1442,11 @@ oslGenericFunction LocaleDataImpl::getFunctionSymbol( const Locale& rLocale, con
 {
     lcl_LookupTableHelper & rLookupTable = lcl_LookupTableStatic::get();
 
-    OUStringBuffer aBuf(1);
     if (cachedItem.get() && cachedItem->equals(rLocale))
     {
-        aBuf.ensureCapacity(strlen(pFunction) + 1 + strlen(cachedItem->localeName));
-        return cachedItem->module->getFunctionSymbol(aBuf.appendAscii(pFunction).append(cUnder).
-                appendAscii(cachedItem->localeName).makeStringAndClear());
+        OString sSymbolName = rtl::OStringView(pFunction) + "_" +
+                cachedItem->localeName;
+        return cachedItem->module->getFunctionSymbol(sSymbolName.getStr());
     }
 
     oslGenericFunction pSymbol = nullptr;
diff --git a/idl/source/cmptools/lex.cxx b/idl/source/cmptools/lex.cxx
index 599b06136008..f479bea4c4b7 100644
--- a/idl/source/cmptools/lex.cxx
+++ b/idl/source/cmptools/lex.cxx
@@ -254,7 +254,7 @@ bool SvTokenStream::MakeToken( SvToken & rToken )
     }
     else if( c == '"' )
     {
-        OStringBuffer aStr;
+        OStringBuffer aStr(128);
         bool bDone = false;
         while( !bDone && !IsEof() && c )
         {
@@ -288,7 +288,7 @@ bool SvTokenStream::MakeToken( SvToken & rToken )
     }
     else if( rtl::isAsciiAlpha (static_cast<unsigned char>(c)) || (c == '_') )
     {
-        OStringBuffer aBuf;
+        OStringBuffer aBuf(64);
         while( rtl::isAsciiAlphanumeric( static_cast<unsigned char>(c) )
                || c == '_' || c == ':')
         {
diff --git a/idl/source/objects/object.cxx b/idl/source/objects/object.cxx
index 4becd0240289..a424bb748044 100644
--- a/idl/source/objects/object.cxx
+++ b/idl/source/objects/object.cxx
@@ -209,7 +209,8 @@ void SvMetaClass::InsertSlots( SvSlotElementList& rList, std::vector<sal_uLong>&
     {
         SvClassElement& rElement = aClassElementList[n];
         SvMetaClass * pCl = rElement.GetClass();
-        OStringBuffer rPre(rPrefix);
+        OStringBuffer rPre(rPrefix.getLength() + 1 + rElement.GetPrefix().getLength());
+        rPre.append(rPrefix);
         if( !rPre.isEmpty() && !rElement.GetPrefix().isEmpty() )
             rPre.append('.');
         rPre.append(rElement.GetPrefix());
diff --git a/idl/source/objects/types.cxx b/idl/source/objects/types.cxx
index d79efe81fc43..34b0e3b78847 100644
--- a/idl/source/objects/types.cxx
+++ b/idl/source/objects/types.cxx
@@ -223,7 +223,7 @@ void SvMetaType::WriteSfxItem(
     WriteStars( rOutStm );
     OString aVarName = " a" + rItemName + "_Impl";
 
-    OStringBuffer aAttrArray;
+    OStringBuffer aAttrArray(1024);
     sal_uLong   nAttrCount = MakeSfx( aAttrArray );
     OString aAttrCount( OString::number(nAttrCount));
     OString aTypeName = "SfxType" + aAttrCount;
diff --git a/idl/source/prj/database.cxx b/idl/source/prj/database.cxx
index f76b38687915..b63205a0911b 100644
--- a/idl/source/prj/database.cxx
+++ b/idl/source/prj/database.cxx
@@ -221,7 +221,7 @@ bool SvIdlDataBase::ReadIdFile( const OString& rOFileName )
             else if( rTok.Is( SvHash_include() ) )
             {
                 rTok = aTokStm.GetToken_Next();
-                OStringBuffer aNameBuf;
+                OStringBuffer aNameBuf(128);
                 if( rTok.IsString() )
                     aNameBuf.append(rTok.GetString());
                 else if( rTok.IsChar() && rTok.GetChar() == '<' )
diff --git a/include/xmlreader/pad.hxx b/include/xmlreader/pad.hxx
index 433b2044300a..d450f7a54c96 100644
--- a/include/xmlreader/pad.hxx
+++ b/include/xmlreader/pad.hxx
@@ -49,7 +49,7 @@ private:
     SAL_DLLPRIVATE void flushSpan();
 
     Span span_;
-    OStringBuffer buffer_;
+    OStringBuffer buffer_ {256};
 };
 
 }
diff --git a/sal/Module_sal.mk b/sal/Module_sal.mk
index 4d7a84ee4e61..b7b3732e3db5 100644
--- a/sal/Module_sal.mk
+++ b/sal/Module_sal.mk
@@ -28,7 +28,6 @@ $(eval $(call gb_Module_add_check_targets,sal,\
 	$(if $(filter WNT,$(OS)),CppunitTest_sal_comtools) \
 	CppunitTest_sal_osl_security \
 	CppunitTest_sal_osl \
-	CppunitTest_sal_rtl \
 	CppunitTest_sal_types \
 ))
 
diff --git a/sal/osl/unx/file_url.cxx b/sal/osl/unx/file_url.cxx
index d149d31e1252..33fcd2952802 100644
--- a/sal/osl/unx/file_url.cxx
+++ b/sal/osl/unx/file_url.cxx
@@ -171,8 +171,8 @@ bool decodeFromUtf8(std::u16string_view text, OString * result) {
     assert(result != nullptr);
     auto p = text.data();
     auto const end = p + text.size();
-    OUStringBuffer ubuf;
-    OStringBuffer bbuf;
+    OUStringBuffer ubuf(static_cast<int>(text.size()));
+    OStringBuffer bbuf(PATH_MAX);
     while (p < end) {
         rtl::uri::detail::EscapeType t;
         sal_uInt32 c = rtl::uri::detail::readUcs4(&p, end, true, RTL_TEXTENCODING_UTF8, &t);
@@ -935,15 +935,16 @@ oslFileError osl::detail::convertUrlToPathname(OUString const & url, OString * p
 
 oslFileError osl::detail::convertPathnameToUrl(OString const & pathname, OUString * url) {
     assert(url != nullptr);
-    OUStringBuffer buf("file:");
+    OUStringBuffer buf(10+pathname.getLength());
+    buf.append("file:");
     if (pathname.startsWith("/")) {
         buf.append("//");
             // so if pathname should ever start with "//" that isn't mistaken for an authority
             // component
     }
     for (sal_Size convert = pathname.getLength();;) {
-        OUStringBuffer ubuf;
         auto n = std::max(convert, sal_Size(PATH_MAX)); // approximation of required converted size
+        OUStringBuffer ubuf(static_cast<int>(n));
         auto s = ubuf.appendUninitialized(n);
         sal_uInt32 info;
         sal_Size converted;
diff --git a/sal/osl/unx/tempfile.cxx b/sal/osl/unx/tempfile.cxx
index cc29a6f59625..84f44cbd4b32 100644
--- a/sal/osl/unx/tempfile.cxx
+++ b/sal/osl/unx/tempfile.cxx
@@ -193,15 +193,17 @@ static oslFileError osl_create_temp_file_impl_(
 
     len_base_dir = rtl_uString_getLength(pustr_base_directory);
 
-    rtl_uStringbuffer_newFromStr_WithLength(
+    rtl_uString_new_WithLength(
         &tmp_file_path,
-        rtl_uString_getStr(const_cast<rtl_uString*>(pustr_base_directory)),
-        len_base_dir);
+        (len_base_dir + 1 + RAND_NAME_LENGTH));
+    capacity = len_base_dir + 1 + RAND_NAME_LENGTH;
 
-    rtl_uStringbuffer_ensureCapacity(
+    rtl_uStringbuffer_insert(
         &tmp_file_path,
         &capacity,
-        (len_base_dir + 1 + RAND_NAME_LENGTH));
+        0,
+        rtl_uString_getStr(const_cast<rtl_uString*>(pustr_base_directory)),
+        len_base_dir);
 
     offset_file_name = len_base_dir;
 
diff --git a/sal/rtl/bootstrap.cxx b/sal/rtl/bootstrap.cxx
index 4417246e9eea..7f5d4317636a 100644
--- a/sal/rtl/bootstrap.cxx
+++ b/sal/rtl/bootstrap.cxx
@@ -800,7 +800,7 @@ void SAL_CALL rtl_bootstrap_expandMacros(rtl_uString ** macro)
 void rtl_bootstrap_encode(rtl_uString const * value, rtl_uString ** encoded)
 {
     OSL_ASSERT(value);
-    OUStringBuffer b;
+    OUStringBuffer b(value->length+5);
     for (sal_Int32 i = 0; i < value->length; ++i)
     {
         sal_Unicode c = value->buffer[i];
@@ -868,7 +868,7 @@ OUString expandMacros(
     ExpandRequestLink const * requestStack)
 {
     SAL_INFO("sal.bootstrap", "expandMacros called with: " << text);
-    OUStringBuffer buf;
+    OUStringBuffer buf(2048);
 
     for (sal_Int32 i = 0; i < text.getLength();)
     {
@@ -975,7 +975,7 @@ OUString expandMacros(
             }
             else
             {
-                OUStringBuffer kbuf;
+                OUStringBuffer kbuf(text.getLength());
                 for (; i < text.getLength();)
                 {
                     sal_Int32 j = i;
diff --git a/sal/rtl/uri.cxx b/sal/rtl/uri.cxx
index ae88e18b8774..592b92c88525 100644
--- a/sal/rtl/uri.cxx
+++ b/sal/rtl/uri.cxx
@@ -638,7 +638,7 @@ void SAL_CALL rtl_uriEncode(rtl_uString * pText, sal_Bool const * pCharClass,
 
     sal_Unicode const * p = pText->buffer;
     sal_Unicode const * pEnd = p + pText->length;
-    sal_Int32 nCapacity = pText->length;
+    sal_Int32 nCapacity = 256;
     rtl_uString_new_WithLength(pResult, nCapacity);
 
     while (p < pEnd)
@@ -758,9 +758,9 @@ sal_Bool SAL_CALL rtl_uriConvertRelToAbs(rtl_uString * pBaseUriRef,
 {
     // Use the strict parser algorithm from RFC 3986, section 5.2, to turn the
     // relative URI into an absolute one:
-    OUStringBuffer aBuffer;
     Components aRelComponents;
     parseUriRef(pRelUriRef, &aRelComponents);
+    OUStringBuffer aBuffer(256);
 
     if (aRelComponents.aScheme.isPresent())
     {
diff --git a/stoc/source/inspect/introspection.cxx b/stoc/source/inspect/introspection.cxx
index b5cebfd268d5..58434b2f51ea 100644
--- a/stoc/source/inspect/introspection.cxx
+++ b/stoc/source/inspect/introspection.cxx
@@ -1438,7 +1438,7 @@ struct TypeKey {
         // the chance of matches between different implementations' getTypes(),
         // but the old scheme of using getImplementationId() would have missed
         // those matches, too:
-        OUStringBuffer b;
+        OUStringBuffer b(static_cast<int>(theTypes.size() * 64));
         for (const css::uno::Type& rType : theTypes) {
             b.append(rType.getTypeName());
             b.append('*'); // arbitrary delimiter not used by type grammar
diff --git a/stoc/source/uriproc/ExternalUriReferenceTranslator.cxx b/stoc/source/uriproc/ExternalUriReferenceTranslator.cxx
index f7b99bf9a8e7..9e21c5aef79f 100644
--- a/stoc/source/uriproc/ExternalUriReferenceTranslator.cxx
+++ b/stoc/source/uriproc/ExternalUriReferenceTranslator.cxx
@@ -92,7 +92,7 @@ OUString Translator::translateToInternal(
         return externalUriReference;
     }
     sal_Int32 i = RTL_CONSTASCII_LENGTH("file:");
-    OUStringBuffer buf;
+    OUStringBuffer buf(128);
     buf.append(std::u16string_view(externalUriReference).substr(0, i));
     // Some environments (e.g., Java) produce illegal file URLs without an
     // authority part; treat them as having an empty authority part:
@@ -140,7 +140,7 @@ OUString Translator::translateToExternal(
         return internalUriReference;
     }
     sal_Int32 i = RTL_CONSTASCII_LENGTH("file://");
-    OUStringBuffer buf;
+    OUStringBuffer buf(128);
     buf.append(std::u16string_view(internalUriReference).substr(0, i));
     rtl_TextEncoding encoding = osl_getThreadTextEncoding();
     for (bool path = true;;) {
diff --git a/stoc/source/uriproc/UriReference.cxx b/stoc/source/uriproc/UriReference.cxx
index dd4d68d3144e..75ed1abaa2a4 100644
--- a/stoc/source/uriproc/UriReference.cxx
+++ b/stoc/source/uriproc/UriReference.cxx
@@ -51,7 +51,7 @@ UriReference::~UriReference() {}
 OUString UriReference::getUriReference()
 {
     osl::MutexGuard g(m_mutex);
-    OUStringBuffer buf;
+    OUStringBuffer buf(128);
     if (!m_scheme.isEmpty()) {
         buf.append(m_scheme);
         buf.append(':');
diff --git a/stoc/source/uriproc/UriReferenceFactory.cxx b/stoc/source/uriproc/UriReferenceFactory.cxx
index 3a5f30b850de..bb96a55d88ed 100644
--- a/stoc/source/uriproc/UriReferenceFactory.cxx
+++ b/stoc/source/uriproc/UriReferenceFactory.cxx
@@ -356,7 +356,7 @@ css::uno::Reference< css::uri::XUriReference > Factory::parse(
     if (n >= 0) {
         scheme = uriReference.copy(0, n);
         schemeSpecificPart = uriReference.copy(n + 1, fragment - (n + 1));
-        OUStringBuffer buf;
+        OUStringBuffer buf(128);
         buf.append("com.sun.star.uri.UriSchemeParser_");
         for (sal_Int32 i = 0; i < scheme.getLength(); ++i) {
             sal_Unicode c = scheme[i];
@@ -488,7 +488,8 @@ css::uno::Reference< css::uri::XUriReference > Factory::makeAbsolute(
         }
         return parse(abs.makeStringAndClear());
     } else {
-        OUStringBuffer abs(baseUriReference->getScheme());
+        OUStringBuffer abs(128);
+        abs.append(baseUriReference->getScheme());
         abs.append(':');
         if (uriReference->hasAuthority()) {
             abs.append("//");
@@ -597,7 +598,7 @@ css::uno::Reference< css::uri::XUriReference > Factory::makeRelative(
                    uriReference->getScheme())) {
         return clone(uriReference);
     } else {
-        OUStringBuffer rel;
+        OUStringBuffer rel(128);
         bool omitQuery = false;
         if ((baseUriReference->hasAuthority() != uriReference->hasAuthority())
             || !equalIgnoreEscapeCase(
diff --git a/stoc/source/uriproc/UriSchemeParser_vndDOTsunDOTstarDOTscript.cxx b/stoc/source/uriproc/UriSchemeParser_vndDOTsunDOTstarDOTscript.cxx
index 1191a711262f..b63fad9d529e 100644
--- a/stoc/source/uriproc/UriSchemeParser_vndDOTsunDOTstarDOTscript.cxx
+++ b/stoc/source/uriproc/UriSchemeParser_vndDOTsunDOTstarDOTscript.cxx
@@ -282,10 +282,9 @@ void SAL_CALL UrlReference::setName(OUString const & name)
     sal_Int32 i = 0;
     parsePart(m_base.m_path, true, &i);
 
-    OUStringBuffer newPath;
-    newPath.append(encodeNameOrParamFragment(name));
-    newPath.append(std::u16string_view(m_base.m_path).substr(i));
-    m_base.m_path = newPath.makeStringAndClear();
+    auto tmp = std::u16string_view(m_base.m_path).substr(i);
+    m_base.m_path = encodeNameOrParamFragment(name) +
+        rtl::OUStringView(tmp.data(), tmp.length());
 }
 
 sal_Bool UrlReference::hasParameter(OUString const & key)
@@ -314,7 +313,7 @@ void UrlReference::setParameter(OUString const & key, OUString const & value)
         i = m_base.m_path.getLength();
     }
 
-    OUStringBuffer newPath;
+    OUStringBuffer newPath(128);
     newPath.append(std::u16string_view(m_base.m_path).substr(0, i));
     if (!bExistent) {
         newPath.append( m_base.m_path.indexOf('?') < 0 ? '?' : '&' );
diff --git a/stoc/source/uriproc/VndSunStarPkgUrlReferenceFactory.cxx b/stoc/source/uriproc/VndSunStarPkgUrlReferenceFactory.cxx
index ff8aa8e84a8e..b6e926bd2e7c 100644
--- a/stoc/source/uriproc/VndSunStarPkgUrlReferenceFactory.cxx
+++ b/stoc/source/uriproc/VndSunStarPkgUrlReferenceFactory.cxx
@@ -94,7 +94,7 @@ Factory::createVndSunStarPkgUrlReference(
             " XVndSunStarPkgUrlReferenceFactory.createVndSunStarPkgUrlReference");
     }
     if (authority->isAbsolute() && !authority->hasFragment()) {
-        OUStringBuffer buf;
+        OUStringBuffer buf(128);
         buf.append("vnd.sun.star.pkg://");
         buf.append(
             rtl::Uri::encode(
diff --git a/stoc/test/uriproc/test_uriproc.cxx b/stoc/test/uriproc/test_uriproc.cxx
index 3cb36343ce32..14132fa70031 100644
--- a/stoc/test/uriproc/test_uriproc.cxx
+++ b/stoc/test/uriproc/test_uriproc.cxx
@@ -82,7 +82,7 @@ OString createTestAssertEqualMessage(
     char const * expectedExpr, char const * actualExpr, T3 const & expected,
     T4 const & actual)
 {
-    OUStringBuffer buf;
+    OUStringBuffer buf(512);
     buf.appendAscii(token1);
     buf.append('|');
     append(buf, token2);
diff --git a/svl/source/numbers/zforlist.cxx b/svl/source/numbers/zforlist.cxx
index 9a0660f74e24..04e32464d8b2 100644
--- a/svl/source/numbers/zforlist.cxx
+++ b/svl/source/numbers/zforlist.cxx
@@ -2719,28 +2719,27 @@ void SvNumberFormatter::ImpGenerateFormats( sal_uInt32 CLOffset, bool bNoAdditio
 
     const NfKeywordTable & rKeyword = pFormatScanner->GetKeywords();
     i18n::NumberFormatCode aSingleFormatCode;
-    OUStringBuffer aBuf;
     aSingleFormatCode.Usage = i18n::KNumberFormatUsage::DATE_TIME;
 
     // YYYY-MM-DD HH:MM:SS   ISO (with blank instead of 'T')
-    aBuf.append( rKeyword[NF_KEY_YYYY]).append('-').
-        append( rKeyword[NF_KEY_MM]).append('-').
-        append( rKeyword[NF_KEY_DD]).append(' ').
-        append( rKeyword[NF_KEY_HH]).append(':').
-        append( rKeyword[NF_KEY_MMI]).append(':').
-        append( rKeyword[NF_KEY_SS]);
-    aSingleFormatCode.Code = aBuf.makeStringAndClear();
+    aSingleFormatCode.Code =
+        rKeyword[NF_KEY_YYYY] + "-" +
+        rKeyword[NF_KEY_MM] + "-" +
+        rKeyword[NF_KEY_DD] + " " +
+        rKeyword[NF_KEY_HH] + ":" +
+        rKeyword[NF_KEY_MMI] + ":" +
+        rKeyword[NF_KEY_SS];
     ImpInsertFormat( aSingleFormatCode,
                      CLOffset + ZF_STANDARD_DATETIME+2 /* NF_DATETIME_ISO_YYYYMMDD_HHMMSS */ );
 
     // YYYY-MM-DD"T"HH:MM:SS   ISO
-    aBuf.append( rKeyword[NF_KEY_YYYY]).append('-').
-        append( rKeyword[NF_KEY_MM]).append('-').
-        append( rKeyword[NF_KEY_DD]).append("\"T\"").
-        append( rKeyword[NF_KEY_HH]).append(':').
-        append( rKeyword[NF_KEY_MMI]).append(':').
-        append( rKeyword[NF_KEY_SS]);
-    aSingleFormatCode.Code = aBuf.makeStringAndClear();
+    aSingleFormatCode.Code =
+        rKeyword[NF_KEY_YYYY] + "-" +
+        rKeyword[NF_KEY_MM] + "-" +
+        rKeyword[NF_KEY_DD] + "\"T\"" +
+        rKeyword[NF_KEY_HH] + ":" +
+        rKeyword[NF_KEY_MMI] + ":" +
+        rKeyword[NF_KEY_SS];
     SvNumberformat* pFormat = ImpInsertFormat( aSingleFormatCode,
                      CLOffset + ZF_STANDARD_DATETIME+3 /* NF_DATETIME_ISO_YYYYMMDDTHHMMSS */ );
     assert(pFormat);
diff --git a/svl/source/numbers/zformat.cxx b/svl/source/numbers/zformat.cxx
index 63a8b5d9e3ab..41db17082089 100644
--- a/svl/source/numbers/zformat.cxx
+++ b/svl/source/numbers/zformat.cxx
@@ -1647,7 +1647,7 @@ short SvNumberformat::ImpNextSymbol(OUStringBuffer& rString,
     sal_Unicode cLetter = ' '; // Preliminary result
     sal_Int32 nLen = rString.getLength();
     ScanState eState = SsStart;
-    OUStringBuffer sBuffSymbol;
+    OUStringBuffer sBuffSymbol(32);
 
     const NfKeywordTable & rKeywords = rScan.GetKeywords();
     while (nPos < nLen && eState != SsStop)
@@ -1975,7 +1975,7 @@ bool SvNumberformat::GetNewCurrencySymbol( OUString& rSymbol,
 // static
 OUString SvNumberformat::StripNewCurrencyDelimiters( const OUString& rStr )
 {
-    OUStringBuffer aTmp;
+    OUStringBuffer aTmp(rStr.getLength());
     sal_Int32 nStartPos, nPos, nLen;
     nLen = rStr.getLength();
     nStartPos = 0;
diff --git a/svx/source/gengal/gengal.cxx b/svx/source/gengal/gengal.cxx
index 90304bea0d14..99e7f4820860 100644
--- a/svx/source/gengal/gengal.cxx
+++ b/svx/source/gengal/gengal.cxx
@@ -200,7 +200,7 @@ static std::vector<OUString> ReadResponseFile_Impl(OUString const& rInput)
     }
 
     std::vector<OUString> ret;
-    OUStringBuffer b;
+    OUStringBuffer b(256);
     char buf[1<<16];
     while (true)
     {
diff --git a/tools/source/fsys/urlobj.cxx b/tools/source/fsys/urlobj.cxx
index 91fe51a9e283..39992a1834ca 100644
--- a/tools/source/fsys/urlobj.cxx
+++ b/tools/source/fsys/urlobj.cxx
@@ -231,9 +231,12 @@ inline sal_Int32 INetURLObject::SubString::clear()
 inline sal_Int32 INetURLObject::SubString::set(OUStringBuffer & rString,
                                        OUString const & rSubString)
 {
-    OUString sTemp(rString.makeStringAndClear());
-    sal_Int32 nDelta = set(sTemp, rSubString);
-    rString.append(sTemp);
+    sal_Int32 nDelta = rSubString.getLength() - m_nLength;
+
+    rString.remove(m_nBegin, m_nLength);
+    rString.insert(m_nBegin, rSubString);
+
+    m_nLength = rSubString.getLength();
     return nDelta;
 }
 
@@ -698,7 +701,7 @@ bool INetURLObject::setAbsURIRef(OUString const & rTheAbsURIRef,
 
     sal_uInt32 nFragmentDelimiter = '#';
 
-    OUStringBuffer aSynAbsURIRef;
+    OUStringBuffer aSynAbsURIRef(rTheAbsURIRef.getLength()*2);
 
     // Parse <scheme>:
     sal_Unicode const * p = pPos;
@@ -949,7 +952,7 @@ bool INetURLObject::setAbsURIRef(OUString const & rTheAbsURIRef,
                     return false;
                 }
                 aSynAbsURIRef.append("//");
-                OUStringBuffer aSynUser;
+                OUStringBuffer aSynUser(128);
 
                 bool bHasUser = false;
                 while (pPos < pEnd && *pPos != '@'
@@ -966,7 +969,7 @@ bool INetURLObject::setAbsURIRef(OUString const & rTheAbsURIRef,
                     bHasUser = *pPos == '@';
                 }
 
-                OUStringBuffer aSynAuthority;
+                OUStringBuffer aSynAuthority(64);
                 if ( !bHasUser )
                 {
                     aSynAuthority = aSynUser;
@@ -2875,7 +2878,7 @@ bool INetURLObject::parsePath(INetProtocol eScheme,
     DBG_ASSERT(pBegin, "INetURLObject::parsePath(): Null output param");
 
     sal_Unicode const * pPos = *pBegin;
-    OUStringBuffer aTheSynPath;
+    OUStringBuffer aTheSynPath(256);
 
     switch (eScheme)
     {
@@ -3267,7 +3270,7 @@ bool INetURLObject::insertName(OUString const & rTheName,
             }
     }
 
-    OUStringBuffer aNewPath;
+    OUStringBuffer aNewPath(256);
     aNewPath.append(pPathBegin, pPrefixEnd - pPathBegin);
     aNewPath.append('/');
     aNewPath.append(encodeText(rTheName, PART_PCHAR,
@@ -3392,7 +3395,7 @@ OUString INetURLObject::decode(sal_Unicode const * pBegin,
         default:
             break;
     }
-    OUStringBuffer aResult;
+    OUStringBuffer aResult(static_cast<int>(pEnd-pBegin));
     while (pBegin < pEnd)
     {
         EscapeType eEscapeType;
@@ -3960,7 +3963,7 @@ bool INetURLObject::removeSegment(sal_Int32 nIndex, bool bIgnoreFinalSlash)
     if (!aSegment.isPresent())
         return false;
 
-    OUStringBuffer aNewPath;
+    OUStringBuffer aNewPath(m_aPath.getLength());
     aNewPath.append(m_aAbsURIRef.getStr() + m_aPath.getBegin(),
                        aSegment.getBegin() - m_aPath.getBegin());
     if (bIgnoreFinalSlash && aSegment.getEnd() == m_aPath.getEnd())
@@ -4159,7 +4162,7 @@ bool INetURLObject::setExtension(OUString const & rTheExtension,
     if (!pExtension)
         pExtension = p;
 
-    OUStringBuffer aNewPath;
+    OUStringBuffer aNewPath(128);
     aNewPath.append(pPathBegin, pExtension - pPathBegin);
     aNewPath.append('.');
     aNewPath.append(encodeText(rTheExtension, PART_PCHAR,
diff --git a/tools/source/inet/inetmime.cxx b/tools/source/inet/inetmime.cxx
index f1c9080996dd..f974c911013c 100644
--- a/tools/source/inet/inetmime.cxx
+++ b/tools/source/inet/inetmime.cxx
@@ -373,7 +373,7 @@ bool parseParameters(ParameterList const & rInput,
                     = getCharsetEncoding(it->m_aCharset.getStr(),
                                                    it->m_aCharset.getStr()
                                                        + it->m_aCharset.getLength());
-            OUStringBuffer aValue;
+            OUStringBuffer aValue(64);
             bool bBadEncoding = false;
             itNext = it;
             do
@@ -715,7 +715,7 @@ sal_Unicode const * scanParameters(sal_Unicode const * pBegin,
         else if (p != pEnd && *p == '"')
             if (pParameters)
             {
-                OStringBuffer aSink;
+                OStringBuffer aSink(256);
                 bool bInvalid = false;
                 for (++p;;)
                 {
diff --git a/tools/source/misc/extendapplicationenvironment.cxx b/tools/source/misc/extendapplicationenvironment.cxx
index 64e1d9801a79..0324a7d0d380 100644
--- a/tools/source/misc/extendapplicationenvironment.cxx
+++ b/tools/source/misc/extendapplicationenvironment.cxx
@@ -47,7 +47,7 @@ void extendApplicationEnvironment() {
 #endif
 
     // Make sure URE_BOOTSTRAP environment variable is set (failure is fatal):
-    OUStringBuffer env;
+    OUStringBuffer env(512);
     OUString envVar("URE_BOOTSTRAP");
     OUString uri;
     if (rtl::Bootstrap::get(envVar, uri))
diff --git a/ucb/source/core/ucb.cxx b/ucb/source/core/ucb.cxx
index 991ea410149d..062db439784b 100644
--- a/ucb/source/core/ucb.cxx
+++ b/ucb/source/core/ucb.cxx
@@ -786,7 +786,7 @@ bool UniversalContentBroker::getContentProviderData(
         uno::Reference< lang::XMultiServiceFactory > xConfigProv =
                 configuration::theDefaultProvider::get( m_xContext );
 
-        OUStringBuffer aFullPath;
+        OUStringBuffer aFullPath(128);
         aFullPath.append(
                 "/org.openoffice.ucb.Configuration/ContentProviders"
                 "/['" );
diff --git a/ucb/source/ucp/inc/urihelper.hxx b/ucb/source/ucp/inc/urihelper.hxx
index 146708c6ee48..19d459181b2f 100644
--- a/ucb/source/ucp/inc/urihelper.hxx
+++ b/ucb/source/ucp/inc/urihelper.hxx
@@ -80,7 +80,7 @@ namespace ucb_impl { namespace urihelper {
                                   rtl_UriEncodeKeepEscapes, /* #i81690# */
                                   RTL_TEXTENCODING_UTF8 );
 
-        OUStringBuffer aResult;
+        OUStringBuffer aResult(256);
         sal_Int32 nIndex = 0;
         do
         {
diff --git a/ucb/source/ucp/webdav-neon/NeonUri.cxx b/ucb/source/ucp/webdav-neon/NeonUri.cxx
index 17db426dcf5b..f7e94b38ddca 100644
--- a/ucb/source/ucp/webdav-neon/NeonUri.cxx
+++ b/ucb/source/ucp/webdav-neon/NeonUri.cxx
@@ -149,7 +149,8 @@ void NeonUri::init( const OString & rUri, const ne_uri * pUri )
 
 void NeonUri::calculateURI ()
 {
-    OUStringBuffer aBuf( mScheme );
+    OUStringBuffer aBuf( 256 );
+    aBuf.append( mScheme );
     aBuf.append( "://" );
     if ( !mUserInfo.isEmpty() )
     {
diff --git a/unoidl/source/sourceprovider-parser.y b/unoidl/source/sourceprovider-parser.y
index 5fb347099ced..d7111d0e3cfa 100644
--- a/unoidl/source/sourceprovider-parser.y
+++ b/unoidl/source/sourceprovider-parser.y
@@ -4028,7 +4028,8 @@ OUString SourceProviderType::getName() const {
         return name;
     case unoidl::detail::SourceProviderType::TYPE_INSTANTIATED_POLYMORPHIC_STRUCT:
         {
-            OUStringBuffer n(name + "<");
+            OUStringBuffer n(512);
+            n.append(name + "<");
             for (auto i(subtypes.begin()); i != subtypes.end(); ++i) {
                 if (i != subtypes.begin()) {
                     n.append(",");
diff --git a/unotools/source/config/pathoptions.cxx b/unotools/source/config/pathoptions.cxx
index 4219c8c44033..b6e5006ce39c 100644
--- a/unotools/source/config/pathoptions.cxx
+++ b/unotools/source/config/pathoptions.cxx
@@ -236,7 +236,7 @@ const OUString& SvtPathOptions_Impl::GetPath( SvtPathOptions::Paths ePath )
                  ePath == SvtPathOptions::PATH_ICONSET)
         {
             auto ctx = comphelper::getProcessComponentContext();
-            OUStringBuffer buf;
+            OUStringBuffer buf(aPathValue.getLength()*2);
             for (sal_Int32 i = 0;;)
             {
                 buf.append(
diff --git a/vcl/source/window/syswin.cxx b/vcl/source/window/syswin.cxx
index c6ecb2109a74..62ceb456c8a6 100644
--- a/vcl/source/window/syswin.cxx
+++ b/vcl/source/window/syswin.cxx
@@ -548,7 +548,7 @@ OString ImplWindowStateToStr(const WindowStateData& rData)
     if ( nValidMask == WindowStateMask::NONE )
         return OString();
 
-    OStringBuffer rStrBuf;
+    OStringBuffer rStrBuf(64);
 
     if ( nValidMask & WindowStateMask::X )
         rStrBuf.append(static_cast<sal_Int32>(rData.GetX()));
diff --git a/xmloff/source/draw/xexptran.cxx b/xmloff/source/draw/xexptran.cxx
index c85022b20ae0..f0a297c935f3 100644
--- a/xmloff/source/draw/xexptran.cxx
+++ b/xmloff/source/draw/xexptran.cxx
@@ -77,7 +77,7 @@ static double Imp_GetDoubleChar(const OUString& rStr, sal_Int32& rPos, const sal
     const SvXMLUnitConverter& rConv, double fRetval, bool bLookForUnits = false)
 {
     sal_Unicode aChar(rStr[rPos]);
-    OUStringBuffer sNumberString;
+    OUStringBuffer sNumberString(32);
 
     if('+' == aChar || '-' == aChar)
     {