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-rw-r--r--CMakeLists.txt53
1 files changed, 45 insertions, 8 deletions
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 61ff9d94..b1753c37 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -796,13 +796,46 @@ endif()
# Check for __attribute__((__ifunc__())) support.
-option(ALLOW_ATTR_IFUNC "Allow use of __attribute__((__ifunc__())) if \
-supported by the system" ON)
+# Supported values for USE_ATTR_IFUNC:
+#
+# auto (default) - Detect ifunc support with a compile test.
+# ON - Always enable ifunc.
+# OFF - Disable ifunc usage.
+set(USE_ATTR_IFUNC "auto" CACHE STRING "Use __attribute__((__ifunc__())).")
+
+set(SUPPORTED_USE_ATTR_IFUNC auto ON OFF)
+
+if(NOT USE_ATTR_IFUNC IN_LIST SUPPORTED_USE_ATTR_IFUNC)
+ message(FATAL_ERROR "'${USE_ATTR_IFUNC}' is not a supported value for"
+ "USE_ATTR_IFUNC")
+endif()
-if(ALLOW_ATTR_IFUNC)
+# When USE_ATTR_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(USE_ATTR_IFUNC STREQUAL "auto")
cmake_push_check_state()
set(CMAKE_REQUIRED_FLAGS "-Werror")
+
check_c_source_compiles("
+ /*
+ * 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)
@@ -817,15 +850,19 @@ if(ALLOW_ATTR_IFUNC)
void make_clang_quiet(void);
void make_clang_quiet(void) { resolve_func()(); }
"
- HAVE_FUNC_ATTRIBUTE_IFUNC)
- cmake_pop_check_state()
- tuklib_add_definition_if(liblzma HAVE_FUNC_ATTRIBUTE_IFUNC)
+ SYSTEM_SUPPORTS_IFUNC)
+
+ cmake_pop_check_state()
+endif()
+
+if(USE_ATTR_IFUNC STREQUAL "ON" OR SYSTEM_SUPPORTS_IFUNC)
+ tuklib_add_definitions(liblzma HAVE_FUNC_ATTRIBUTE_IFUNC)
- if(HAVE_FUNC_ATTRIBUTE_IFUNC AND CMAKE_C_FLAGS MATCHES "-fsanitize=")
+ if(CMAKE_C_FLAGS MATCHES "-fsanitize=")
message(SEND_ERROR
"CMAKE_C_FLAGS or the environment variable CFLAGS "
"contains '-fsanitize=' which is incompatible "
- "with ifunc. Use -DALLOW_ATTR_IFUNC=OFF "
+ "with ifunc. Use -DUSE_ATTR_IFUNC=OFF "
"as an argument to 'cmake' when using '-fsanitize'.")
endif()
endif()