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| author | serge-sans-paille <sguelton@redhat.com> | 2022-06-28 11:01:55 +0200 |
|---|---|---|
| committer | serge-sans-paille <sguelton@redhat.com> | 2022-07-18 12:45:52 +0200 |
| commit | f764dc99b37e1e6428724a61f36bcb49c015dc70 (patch) | |
| tree | 63232db1fb62062e17a95f4cbaf5e562d3304432 /clang/docs | |
| parent | 432cbd7827202e4316225820f3f90417b9fcce6c (diff) | |
| download | llvm-f764dc99b37e1e6428724a61f36bcb49c015dc70.zip llvm-f764dc99b37e1e6428724a61f36bcb49c015dc70.tar.gz llvm-f764dc99b37e1e6428724a61f36bcb49c015dc70.tar.bz2 | |
[clang] Introduce -fstrict-flex-arrays=<n> for stricter handling of flexible arrays
Some code [0] consider that trailing arrays are flexible, whatever their size.
Support for these legacy code has been introduced in
f8f632498307d22e10fab0704548b270b15f1e1e but it prevents evaluation of
__builtin_object_size and __builtin_dynamic_object_size in some legit cases.
Introduce -fstrict-flex-arrays=<n> to have stricter conformance when it is
desirable.
n = 0: current behavior, any trailing array member is a flexible array. The default.
n = 1: any trailing array member of undefined, 0 or 1 size is a flexible array member
n = 2: any trailing array member of undefined or 0 size is a flexible array member
This takes into account two specificities of clang: array bounds as macro id
disqualify FAM, as well as non standard layout.
Similar patch for gcc discuss here: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836
[0] https://docs.freebsd.org/en/books/developers-handbook/sockets/#sockets-essential-functions
Diffstat (limited to 'clang/docs')
| -rw-r--r-- | clang/docs/ClangCommandLineReference.rst | 6 | ||||
| -rw-r--r-- | clang/docs/ReleaseNotes.rst | 4 |
2 files changed, 10 insertions, 0 deletions
diff --git a/clang/docs/ClangCommandLineReference.rst b/clang/docs/ClangCommandLineReference.rst index 216872b..223990e 100644 --- a/clang/docs/ClangCommandLineReference.rst +++ b/clang/docs/ClangCommandLineReference.rst @@ -2647,6 +2647,12 @@ Enable unstable and experimental features .. option:: -fuse-init-array, -fno-use-init-array +.. option:: -fstrict-flex-arrays=<arg>, -fno-strict-flex-arrays + +Control which arrays are considered as flexible arrays members. <arg> +can be 1 (array of size 0, 1 and undefined are considered) or 2 (array of size 0 +and undefined are considered). + .. option:: -fuse-ld=<arg> .. option:: -fuse-line-directives, -fno-use-line-directives diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 17c1dac..cb64cd2 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -68,6 +68,10 @@ Major New Features Randomizing structure layout is a C-only feature. +- Clang now supports the ``-fstrict-flex-arrays=<arg>`` option to control which + array bounds lead to flexible array members. The option yields more accurate + ``__builtin_object_size`` and ``__builtin_dynamic_object_size`` results in + most cases but may be overly conservative for some legacy code. - Experimental support for HLSL has been added. The implementation is incomplete and highly experimental. For more information about the ongoing work to support HLSL see the `documentation |