[PATCH v2] linux: Fix a non-constant expression in _Static_assert

Fangrui Song maskray@google.com
Fri Oct 8 00:46:43 GMT 2021


According to C11 6.6p6, `const int` as an operand may not make up a
constant expression. GCC -O0 errors:

../sysdeps/unix/sysv/linux/opendir.c:107:19: error: static_assert expression is not an integral constant expression
  _Static_assert (allocation_size >= sizeof (struct dirent64),

-O2 -Wpedantic has a similar warning.
See https://gcc.gnu.org/PR102502 for GCC's inconsistency.

Use enum which is guaranteed to be a constant expression.
This also makes the file compilable with Clang.

Fixes: 4b962c9e859de23b461d61f860dbd3f21311e83a ("linux: Simplify opendir buffer allocation")
---
Changes from v1:
* Clarify commit message
* Reference https://gcc.gnu.org/PR102502 
---
 sysdeps/unix/sysv/linux/opendir.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sysdeps/unix/sysv/linux/opendir.c b/sysdeps/unix/sysv/linux/opendir.c
index 48f254d169..88640f44ee 100644
--- a/sysdeps/unix/sysv/linux/opendir.c
+++ b/sysdeps/unix/sysv/linux/opendir.c
@@ -103,7 +103,7 @@ __alloc_dir (int fd, bool close_fd, int flags,
      file system provides a bogus value.  */
   enum { max_buffer_size = 1048576 };
 
-  const size_t allocation_size = 32768;
+  enum { allocation_size = 32768 };
   _Static_assert (allocation_size >= sizeof (struct dirent64),
 		  "allocation_size < sizeof (struct dirent64)");
 
-- 
2.33.0.882.g93a45727a2-goog



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