[Guile-commits] 04/04: build: Test '-flto' on both compiler and linker.

[Ludovic Courtès]

civodul pushed a commit to branch main
in repository guile.

commit f047133e7b43433e77dc01741d559ac9e2a9ea58
Author: Sergei Trofimovich <slyich@gmail.com>
AuthorDate: Sun Feb 20 09:39:59 2022 +0000

    build: Test '-flto' on both compiler and linker.
    
    Before the change ./configure incorrectly enabled -flto on toolchains
    that support -flto on compiler side but don't support -flto on linker
    side. This caused incorrect type size detection on nixpkgs' Darwin:
    
     configure:54594: checking size of size_t
     configure:54600: clang -std=gnu11 -o conftest -g -O2 -flto   conftest.c  
>&5
     ld: warning: ignoring file 
/private/tmp/nix-build-guile-3.0.8.drv-0/conftest-00e93d.o,
       building for macOS-x86_64 but attempting to link with file built
       for unknown-unsupported file format ( 0xDE 0xC0 0x17 0x0B 0x00 0x00 0x00 
0x00 0x14 0x00 0x00 0x00 0x80 0x1A 0x00 0x00 )
     Undefined symbols for architecture x86_64:
       "_main", referenced from:
          implicit entry/start for main executable
     ld: symbol(s) not found for architecture x86_64
     clang-11: error: linker command failed with exit code 1 (use -v to see 
invocation)
    
    Taken from 
https://github.com/NixOS/nixpkgs/pull/160051#issuecomment-1046105041
    
    The change makes sure -flto support tests basic support of just for
    object file generation but for linker as well.
    
    * configure.ac: use AC_LINK_IFELSE instead of AC_COMPILE_IFELSE.
    
    Signed-off-by: Ludovic Courtès <ludo@gnu.org>
---
 NEWS         | 1 +
 configure.ac | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index 0c77f8dd7..b0217a429 100644
--- a/NEWS
+++ b/NEWS
@@ -13,6 +13,7 @@ Changes in 3.0.9 (since 3.0.8)
    (https://bugs.gnu.org/54198)
 ** psyntax honors source properties coming from read hash extensions
    (https://bugs.gnu.org/54003)
+** ./configure checks whether the linker supports '-flto' (needed on macOS)
 
 
 Changes in 3.0.8 (since 3.0.7)
diff --git a/configure.ac b/configure.ac
index ad7ff12c6..30229489d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -69,7 +69,7 @@ AC_MSG_CHECKING([whether the compiler supports -flto])
 old_CFLAGS="$CFLAGS"
 LTO_CFLAGS="-flto"
 CFLAGS="$CFLAGS $LTO_CFLAGS"
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([int foo;])],, [LTO_CFLAGS=])
+AC_LINK_IFELSE([AC_LANG_PROGRAM([int foo;], [])],, [LTO_CFLAGS=])
 CFLAGS="$old_CFLAGS"
 if test -n "$LTO_CFLAGS"; then
   AC_MSG_RESULT([yes])