libtool.m4: Avoid a broken AC_TRY_EVAL macro

As said in the Autoconf source, the AC_TRY_EVAL macro is dangerous and
undocumented, and should not be used.
In particular, the one related to nm yields binary data in the config.log
file with dash, where "echo \\1" (echo with the argument \1) produces the
control character ^A instead of the usual \1 with most shells (POSIX says
that the result is implementation-defined). See:
  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=910076
This patch attempts to replace this AC_TRY_EVAL occurrence by code with
similar behavior, but using $ECHO instead of echo in order to avoid the
backslash issue.

https://debbugs.gnu.org/cgi/bugreport.cgi?bug=21309

diff --git a/m4/libtool.m4 b/m4/libtool.m4
index 87ca4672175c5b416fab5896b70c444abfba0661..322ca1fe06436ebe704e203e79187baad3961209 100644 (file)
--- a/m4/libtool.m4
+++ b/m4/libtool.m4
@@ -4129,7 +4129,8 @@ _LT_EOF
   if AC_TRY_EVAL(ac_compile); then
     # Now try to grab the symbols.
     nlist=conftest.nm
-    if AC_TRY_EVAL(NM conftest.$ac_objext \| "$lt_cv_sys_global_symbol_pipe" \> $nlist) && test -s "$nlist"; then
+    $ECHO "$as_me:$LINENO: $NM conftest.$ac_objext | $lt_cv_sys_global_symbol_pipe > $nlist" >&AS_MESSAGE_LOG_FD
+    if eval "$NM" conftest.$ac_objext \| "$lt_cv_sys_global_symbol_pipe" \> $nlist 2>&AS_MESSAGE_LOG_FD && test -s "$nlist"; then
       # Try sorting and uniquifying the output.
       if sort "$nlist" | uniq > "$nlist"T; then
        mv -f "$nlist"T "$nlist"