diff options
| author | Stephan Bergmann <sbergman@redhat.com> | 2021-04-23 13:28:37 +0200 |
|---|---|---|
| committer | Stephan Bergmann <sbergman@redhat.com> | 2021-04-23 19:06:05 +0200 |
| commit | 8ae3ae4bf75fdd0aaa132c956d9da029baa3adc6 (patch) | |
| tree | 0075cabf07b9d896083ab8c9b973c3786581ea2f /sal | |
| parent | 87bd31e28cb0688acb2d05f99daeea038bfe38fc (diff) | |
Step 1 of removing cargo-cult pragma pack around rtl_[u]String
Following up on f62cb40bdfaf41cf8e989640f9be79f652f30914 "Remove dubious #pragma
pack" and 9eba8aa38db3a0dc2f7dfaf24a003c16418aef18 "Remove dubious #pragma pack"
for O[U]StringLiteral, which argued that the pragma pack around rtl_[u]String
are useless cargo cult (paraphrasing): "All struct member types involved
(oslInterlockedCount aka sal_Int32, sal_Int32 itself, sal_Unicode, and char)
have size <= 4 resp. < 8, so the member alignment ("on a boundary that's either
a multiple of [the pragma pack value], or a multiple of the size of the member,
whichever is smaller", according to
<https://docs.microsoft.com/en-us/cpp/preprocessor/pack?view=msvc-160>) is not
affected. And neither are alignof(rtl_String) and alignof(rtl_uString)
affected, which would remain e.g. 4 on x86-64."
(Curiously, the pragma pack value had always been 8 for rtl_String but 4 for
rtl_uString, ever since at least 9399c662f36c385b0c705eb34e636a9aec450282
"initial import".)
The plan is as follows: In step 1, add temporary static_asserts that state the
current alignof/sizeof values; keep this for a while to see that all relevant
Windows builds actually agree on these status-quo values. In step 2, remove the
pragma pack cargo cult; keep the static_asserts for a while to see that the
removal has no impact on any of the relevant Windows builds. Finally, in
step 3, remove the temporary static_asserts again.
Change-Id: I8059ac300cc5b517db4a575f0eaba48678966537
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/114540
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
Diffstat (limited to 'sal')
| -rw-r--r-- | sal/rtl/string.cxx | 7 | ||||
| -rw-r--r-- | sal/rtl/ustring.cxx | 7 |
2 files changed, 14 insertions, 0 deletions
diff --git a/sal/rtl/string.cxx b/sal/rtl/string.cxx index a649406f68ad..94be8029032a 100644 --- a/sal/rtl/string.cxx +++ b/sal/rtl/string.cxx @@ -33,6 +33,13 @@ #include <rtl/math.h> +#if defined _WIN32 +// Temporary check to verify that the #pragma pack around rtl_String is indeed cargo cult and can +// safely be removed: +static_assert(alignof (rtl_String) == 4); +static_assert(sizeof (rtl_String) == 12); +#endif + /* ======================================================================= */ #if USE_SDT_PROBES diff --git a/sal/rtl/ustring.cxx b/sal/rtl/ustring.cxx index a5efa62d759c..4aac64556666 100644 --- a/sal/rtl/ustring.cxx +++ b/sal/rtl/ustring.cxx @@ -42,6 +42,13 @@ #include <rtl/math.h> +#if defined _WIN32 +// Temporary check to verify that the #pragma pack around rtl_uString is indeed cargo cult and can +// safely be removed: +static_assert(alignof (rtl_uString) == 4); +static_assert(sizeof (rtl_uString) == 12); +#endif + /* ======================================================================= */ #if USE_SDT_PROBES |