Thanks Bruce for the details about the .la file.
> If ./configure is run with --prefix=/usr with both libsigsegv and
> /usr/lib/libc.a are present, configure gives:
>
> configure:10063: checking for libsigsegv
> configure:10086: gcc -o conftest -g -O2 conftest.c
> /usr/lib/libsigsegv.so /usr/lib/libc.a >&5
> configure:10086: $? = 0
> configure:10097: result: yes
> configure:10104: checking how to link with libsigsegv
> configure:10106: result: /usr/lib/libsigsegv.so /usr/lib/libc.a
>
> Which causes grep to segfault immediately.
Whereas on an Ubuntu 16.04 system the effect is weird in a different sense:
the compilation fails with an error
/usr/bin/ld: dynamic STT_GNU_IFUNC symbol `strcmp' with pointer equality in
`/usr/lib/libc.a(strcmp.o)' can not be used when making an executable;
recompile with -fPIE and relink with -pie
leading to
checking for libsigsegv... no
> If I move all libtool .la files (I really dislike libtool) out of the
> way
The .la file contains a comment
# Please DO NOT delete this file!
# It is necessary for linking the library.
but in fact all distros I know of don't distribute .la files. Go figure.
The patch below should fix it.
2020-09-19 Bruno Haible <br...@clisp.org>
havelib: Avoid linking with libc.a on GNU systems.
Reported by Bruce Dubbs <bruce.du...@gmail.com> in
<https://lists.gnu.org/archive/html/grep-devel/2020-09/msg00052.html>.
* m4/lib-link.m4 (AC_LIB_LINKFLAGS_BODY): When processing the
dependency_libs value of a .la file, ignore '-lc' options on GNU
systems.
diff --git a/m4/lib-link.m4 b/m4/lib-link.m4
index eecf70e..5ce1aa2 100644
--- a/m4/lib-link.m4
+++ b/m4/lib-link.m4
@@ -1,4 +1,4 @@
-# lib-link.m4 serial 31
+# lib-link.m4 serial 32
dnl Copyright (C) 2001-2020 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
@@ -631,7 +631,20 @@ AC_DEFUN([AC_LIB_LINKFLAGS_BODY],
;;
-l*)
dnl Handle this in the next round.
- names_next_round="$names_next_round "`echo "X$dep" | sed
-e 's/^X-l//'`
+ dnl But on GNU systems, ignore -lc options, because
+ dnl - linking with libc is the default anyway,
+ dnl - linking with libc.a may produce an error
+ dnl "/usr/bin/ld: dynamic STT_GNU_IFUNC symbol
`strcmp' with pointer equality in `/usr/lib/libc.a(strcmp.o)' can not be used
when making an executable; recompile with -fPIE and relink with -pie"
+ dnl or may produce an executable that always crashes,
see
+ dnl
<https://lists.gnu.org/archive/html/grep-devel/2020-09/msg00052.html>.
+ dep=`echo "X$dep" | sed -e 's/^X-l//'`
+ if test "X$dep" != Xc \
+ || case $host_os in
+ linux* | gnu* | k*bsd*-gnu) false ;;
+ *) true ;;
+ esac; then
+ names_next_round="$names_next_round $dep"
+ fi
;;
*.la)
dnl Handle this in the next round. Throw away the .la's
