liblzma: Remove ifunc support.

This is *NOT* done for security reasons even though the backdoor
relied on the ifunc code. Instead, the reason is that in this
project ifunc provides little benefits but it's quite a bit of
extra code to support it. The only case where ifunc *might* matter
for performance is if the CRC functions are used directly by an
application. In normal compression use it's completely irrelevant.

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.