1760effa33
This commit implements gcc_struct attribute with the behavior similar to
one in GCC. Current behavior is as follows:
When ItaniumRecordLayoutBuilder is used, [[gcc_struct]] will locally
cancel the effect of -mms-bitfields on a record. If -mms-bitfields is
not supplied and is not a default behavior on a target, [[gcc_struct]]
will be a no-op. This should provide enough compatibility with GCC.
If C++ ABI is "Microsoft", [[gcc_struct]] will currently always produce
a diagnostic, since support for it is not yet implemented in
MicrosoftRecordLayoutBuilder. Note, however, that all the infrastructure
is ready for the future implementation.
In particular, check for default value of -mms-bitfields is moved from a
driver to ASTContext, since it now non-trivially depends on other
supplied flags. This also, unfortunately, makes it impossible to use
usual argument parsing for `-m{no-,}ms-bitfields`.
The patch doesn't introduce any backwards-incompatible changes, except
for situations when cc1 is called directly with `-mms-bitfields` option.
Work towards #24757
---------
Co-authored-by: Martin Storsjö <martin@martin.st>
7 lines
236 B
C
7 lines
236 B
C
// RUN: %clang_cc1 -emit-llvm-only -triple x86_64-pc-windows-msvc -fms-layout-compatibility=itanium -verify %s
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// expected-error@+1 {{Itanium-compatible layout for the Microsoft C++ ABI is not yet supported}}
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struct {
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int a;
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} t1;
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