diff options
Diffstat (limited to '')
| -rw-r--r-- | configure.ac | 79 |
1 files changed, 0 insertions, 79 deletions
diff --git a/configure.ac b/configure.ac index fb4f3d66..b6f9f8b7 100644 --- a/configure.ac +++ b/configure.ac @@ -893,85 +893,6 @@ if test "x$enable_small$enable_threads$have_func_attribute_constructor" \ __attribute__((__constructor__))]) fi -# __attribute__((__ifunc__())) can be used to choose between different -# implementations of the same function at runtime. This is slightly more -# efficient than using __attribute__((__constructor__)) and setting -# a function pointer. -AC_ARG_ENABLE([ifunc], [AS_HELP_STRING([--enable-ifunc], - [Use __attribute__((__ifunc__())). Enabled by default on - GNU/Linux (glibc) and FreeBSD.])], - [], [enable_ifunc=auto]) - -# When enable_ifunc is 'auto', allow the use of __attribute__((__ifunc__())) -# if compiler support is detected and we are building for GNU/Linux (glibc) -# or FreeBSD. uClibc and musl don't support ifunc in their dynamic linkers -# but some compilers still accept the attribute when compiling for these -# C libraries, which results in broken binaries. That's why we need to -# check which libc is being used. -if test "x$enable_ifunc" = xauto ; then - OLD_CFLAGS="$CFLAGS" - CFLAGS="$CFLAGS -Werror" - AC_MSG_CHECKING([if __attribute__((__ifunc__())) can be used]) - AC_COMPILE_IFELSE([AC_LANG_SOURCE([[ - /* - * Force a compilation error when not using glibc on Linux - * or if we are not using FreeBSD. uClibc will define - * __GLIBC__ but does not support ifunc, so we must have - * an extra check to disable with uClibc. - */ - #if defined(__linux__) - # include <features.h> - # if !defined(__GLIBC__) || defined(__UCLIBC__) - compile error - # endif - #elif !defined(__FreeBSD__) - compile error - #endif - - static void func(void) { return; } - - /* - * The attribute __no_profile_instrument_function__ is - * needed with GCC to prevent improper instrumentation in - * the ifunc resolver. - */ - __attribute__((__no_profile_instrument_function__)) - static void (*resolve_func (void)) (void) { return func; } - void func_ifunc (void) - __attribute__((__ifunc__("resolve_func"))); - /* - * 'clang -Wall' incorrectly warns that resolve_func is - * unused (-Wunused-function). Correct assembly output is - * still produced. This problem exists at least in Clang - * versions 4 to 17. The following silences the bogus warning: - */ - void make_clang_quiet(void); - void make_clang_quiet(void) { resolve_func()(); } - ]])], [ - enable_ifunc=yes - ], [ - enable_ifunc=no - ]) - - AC_MSG_RESULT([$enable_ifunc]) - - CFLAGS="$OLD_CFLAGS" -fi - -if test "x$enable_ifunc" = xyes ; then - AC_DEFINE([HAVE_FUNC_ATTRIBUTE_IFUNC], [1], - [Define to 1 if __attribute__((__ifunc__())) - is supported for functions.]) - - # ifunc explicitly does not work with -fsanitize=address. - # If configured, it will result in a liblzma build that will fail - # when liblzma is loaded at runtime (when the ifunc resolver - # executes). - AS_CASE([$CFLAGS], [*-fsanitize=*], [AC_MSG_ERROR([ - CFLAGS contains '-fsanitize=' which is incompatible with ifunc. - Use --disable-ifunc when using '-fsanitize'.])]) -fi - ############################################################################### # Checks for library functions. |