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Build: Use AC_LINK_IFELSE instead of -Werror 

AC_COMPILE_IFELSE needed -Werror because Clang <= 14 would merely
warn about the unsupported attribute and implicit function declaration.
Changing to AC_LINK_IFELSE handles the implicit declaration because
the symbol __crc32d is unlikely to exist in libc.

Note that the other part of the check is that #include <arm_acle.h>
must work. If the header is missing, most compilers give an error
and the linking step won't be attempted.

Avoiding -Werror makes the check more robust in case CFLAGS contains
warning flags that break -Werror anyway (but this isn't the only check
in configure.ac that has this problem). Using AC_LINK_IFELSE also makes
the check more similar to how it is done in CMakeLists.txt.
This commit is contained in:
Lasse Collin 2024-06-24 23:35:59 +03:00
parent 5a728813c3
commit 35eb57355a
1 changed files with 1 additions and 11 deletions
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12
configure.ac
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@ -1059,15 +1059,7 @@ AC_MSG_CHECKING([if ARM64 CRC32 instruction is usable])
AS_IF([test "x$enable_arm64_crc32" = xno], [
AC_MSG_RESULT([no, --disable-arm64-crc32 was used])
], [
# Set -Werror here because some versions of Clang (14 and older)
# do not report the unsupported __attribute__((__target__("+crc")))
# or __crc32d() as an error, only as a warning. This does not need
# to be done with CMake because tests will attempt to link and the
# error will be reported then.
OLD_CFLAGS="$CFLAGS"
CFLAGS="$CFLAGS -Werror"
AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
AC_LINK_IFELSE([AC_LANG_SOURCE([[
#include <arm_acle.h>
#include <stdint.h>
@ -1087,8 +1079,6 @@ int main(void)
enable_arm64_crc32=no
])
AC_MSG_RESULT([$enable_arm64_crc32])
CFLAGS="$OLD_CFLAGS"
])
# Check for ARM64 CRC32 instruction runtime detection.