Merge pull request #1625 from evelikov/gc-sections

Instrument gcc/clang to discard unused code during link

1 files changed, 16 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index 85868ade..f9fe624e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -542,6 +542,22 @@ fi
 # Checks for supported compiler flags
 AX_APPEND_COMPILE_FLAGS([-Wall -Wformat -Wformat-security])
 
+# Place the functions and data into separate sections, allowing the linker
+# to garbage collect the unused ones.
+save_LDFLAGS=$LDFLAGS
+LDFLAGS="$LDFLAGS -Wl,--gc-sections"
+AC_MSG_CHECKING([whether ld supports --gc-sections])
+AC_LINK_IFELSE(
+    [AC_LANG_SOURCE([static char UnusedFunc() { return 5; } int main() { return 0;}])],
+    [AC_MSG_RESULT([yes])
+        GC_SECTIONS="-Wl,--gc-sections";
+        AX_APPEND_COMPILE_FLAGS([-ffunction-sections -fdata-sections])],
+    [AC_MSG_RESULT([no])
+        GC_SECTIONS="";])
+LDFLAGS=$save_LDFLAGS
+
+AC_SUBST(GC_SECTIONS)
+
 # Checks for typedefs, structures, and compiler characteristics.
 AC_C_CONST
 # la_TYPE_UID_T defaults to "int", which is incorrect for MinGW