stack-trace: Fix compilation errors on older BSD systems

[Bruno Haible]

While the gnulib CI is "green", building a testdir on older BSD platforms leads 
to compilation errors.

For example, on OpenBSD 6.0, most compilation units fail to compile with these 
errors:

gcc -std=gnu99 -DHAVE_CONFIG_H -DEXEEXT=\"\" -DEXEEXT=\"\" -DNO_XMALLOC 
-DEXEEXT=\"\" -I. -I../../gllib -I..  -DGNULIB_STRICT_CHECKING=1 
-I/home/bruno/include -Wall -fvisibility=hidden -g -O2 -MT argmatch.o -MD -MP 
-MF $depbase.Tpo -c -o argmatch.o ../../gllib/argmatch.c &&\
mv -f $depbase.Tpo $depbase.Po
In file included from ./sys/select.h:102,
                 from /usr/include/sys/types.h:230,
                 from ./sys/types.h:46,
                 from /usr/include/stdio.h:45,
                 from ./stdio.h:55,
                 from ../../gllib/argmatch.h:32,
                 from ../../gllib/argmatch.c:25:
./sys/time.h:651: error: conflicting types for 'gettimeofday'
/usr/include/sys/time.h:344: error: previous declaration of 'gettimeofday' was 
here
In file included from ./sys/select.h:131,
                 from /usr/include/sys/types.h:230,
                 from ./sys/types.h:46,
                 from /usr/include/stdio.h:45,
                 from ./stdio.h:55,
                 from ../../gllib/argmatch.h:32,
                 from ../../gllib/argmatch.c:25:
./signal.h:797: error: size of array 'verify_NSIG_constraint' is negative
./signal.h:1025: error: redefinition of 'struct sigaction'
gmake[4]: *** [Makefile:11884: argmatch.o] Error 1

The cause is that at configure time, all "checking for <function>" tests fail 
with
/usr/bin/ld: cannot find -lexecinfo

This patch fixes it.


2024-12-28  Bruno Haible  <bruno@clisp.org>

        stack-trace: Fix compilation errors on older BSD systems.
        * m4/stack-trace.m4 (gl_STACK_TRACE_EARLY): Test whether we can link
        with libexecinfo before modifying LIBS.

diff --git a/m4/stack-trace.m4 b/m4/stack-trace.m4
index 2267fcbb81..39106683fd 100644
--- a/m4/stack-trace.m4
+++ b/m4/stack-trace.m4
@@ -1,5 +1,5 @@
 # stack-trace.m4
-# serial 3
+# serial 4
 dnl Copyright (C) 2024 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -57,19 +57,27 @@ AC_DEFUN([gl_STACK_TRACE_EARLY]
         *-gnu* | gnu* | darwin* | freebsd* | dragonfly* | netbsd* | openbsd* | 
solaris*)
           dnl execinfo might be implemented on this platform.
           CAN_PRINT_STACK_TRACE=1
-          dnl On *BSD system, link all programs with -lexecinfo. Cf. 
m4/execinfo.m4.
+          dnl On *BSD system, link all programs with -lexecinfo, provided that
+          dnl libexecinfo actually exists. Cf. m4/execinfo.m4.
           case "$host_os" in
             freebsd* | dragonfly* | netbsd* | openbsd*)
-              LIBS="$LIBS -lexecinfo"
-              ;;
-          esac
-          dnl Link all programs in such a way that the stack trace includes the
-          dnl function names. '-rdynamic' is equivalent to 
'-Wl,-export-dynamic'.
-          case "$host_os" in
-            *-gnu* | gnu* | openbsd*)
-              LDFLAGS="$LDFLAGS -rdynamic"
+              AC_SEARCH_LIBS([backtrace_symbols_fd], [execinfo],
+                [], [CAN_PRINT_STACK_TRACE=0])
+              if test $CAN_PRINT_STACK_TRACE = 1; then
+                LIBS="$LIBS -lexecinfo"
+              fi
               ;;
           esac
+          if test $CAN_PRINT_STACK_TRACE = 1; then
+            dnl Link all programs in such a way that the stack trace includes
+            dnl the function names.
+            dnl '-rdynamic' is equivalent to '-Wl,-export-dynamic'.
+            case "$host_os" in
+              *-gnu* | gnu* | openbsd*)
+                LDFLAGS="$LDFLAGS -rdynamic"
+                ;;
+            esac
+          fi
           ;;
       esac
     fi