diff options
| -rw-r--r-- | configure.ac | 61 |
1 files changed, 44 insertions, 17 deletions
diff --git a/configure.ac b/configure.ac index 1fe61016..cdd72a9f 100644 --- a/configure.ac +++ b/configure.ac @@ -869,15 +869,37 @@ fi # 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([--disable-ifunc], - [do not use __attribute__((__ifunc__()))])], - [], [enable_ifunc=yes]) - -if test "x$enable_ifunc" = xyes ; then +AC_ARG_ENABLE([ifunc], [AS_HELP_STRING([--enable-ifunc], + [Use __attribute__((__ifunc__())). Enabled by default on + GNU/Linux (glibc) and FreeBSD.])], + [], [enable_ifunc=auto]) + +# When enable_ifunc is 'auto', allow the use of __attribute__((__ifunc__())) +# if compiler support is detected and we are building for GNU/Linux (glibc) +# or FreeBSD. uClibc and musl don't support ifunc in their dynamic linkers +# but some compilers still accept the attribute when compiling for these +# C libraries, which results in broken binaries. That's why we need to +# check which libc is being used. +if test "x$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; } static void (*resolve_func (void)) (void) { return func; } void func_ifunc (void) @@ -891,23 +913,28 @@ if test "x$enable_ifunc" = xyes ; then void make_clang_quiet(void); void make_clang_quiet(void) { resolve_func()(); } ]])], [ - AC_DEFINE([HAVE_FUNC_ATTRIBUTE_IFUNC], [1], + enable_ifunc=yes + ], [ + enable_ifunc=no + ]) + + AC_MSG_RESULT([$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.]) - AC_MSG_RESULT([yes]) - # 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([$CFLAGS], [*-fsanitize=*], [AC_MSG_ERROR([ + # ifunc explicitly does not work with -fsanitize=address. + # If configured, it will result in a liblzma build that will fail + # when liblzma is loaded at runtime (when the ifunc resolver + # executes). + AS_CASE([$CFLAGS], [*-fsanitize=*], [AC_MSG_ERROR([ CFLAGS contains '-fsanitize=' which is incompatible with ifunc. Use --disable-ifunc when using '-fsanitize'.])]) - ], [ - AC_MSG_RESULT([no]) - ]) - - CFLAGS="$OLD_CFLAGS" fi |