From 5dcb7cd3cb63bf8a3a5f7531d10f937053930a25 Mon Sep 17 00:00:00 2001
From: Tony Kelman <tony@kelman.net>
Date: Sun, 31 Jan 2016 08:31:04 +0000
Subject: [PATCH] Fix compilation of tests on alpine linux (musl libc)

If we don't link to libexecinfo, as detected by the
AC_SEARCH_LIBS(backtrace, execinfo) configure probe, we get

```
test-coredump-unwind.o: In function `handle_sigsegv':
/home/libunwind/tests/test-coredump-unwind.c:246: undefined reference to
`backtrace_symbols_fd'
collect2: error: ld returned 1 exit status
Makefile:1187: recipe for target 'test-coredump-unwind' failed
```

and

```
Gtest-init.o: In function `do_backtrace()':
Gtest-init.cxx:(.text+0x2f): undefined reference to `_Ux86_64_getcontext'
Gtest-init.cxx:(.text+0x48): undefined reference to `_Ux86_64_init_local'
Gtest-init.cxx:(.text+0x63): undefined reference to `_Ux86_64_get_reg'
Gtest-init.cxx:(.text+0x96): undefined reference to `_Ux86_64_get_proc_name'
Gtest-init.cxx:(.text+0x171): undefined reference to `_Ux86_64_step'
collect2: error: ld returned 1 exit status
Makefile:1063: recipe for target 'Gtest-init' failed
```

There are 2 XFAIL and 6 FAIL tests, but it's a start
---
 configure.ac      | 5 +++++
 tests/Makefile.am | 4 ++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index 6c46cf35..21bae907 100644
--- a/configure.ac
+++ b/configure.ac
@@ -373,6 +373,10 @@ old_LIBS="$LIBS"
 LIBS=""
 AC_SEARCH_LIBS(backtrace, execinfo)
 LIBS="$old_LIBS"
+case "$ac_cv_search_backtrace" in
+  -l*) BACKTRACELIB=$ac_cv_search_backtrace;;
+  *) BACKTRACELIB="";;
+esac
 
 AC_SUBST(build_arch)
 AC_SUBST(target_os)
@@ -388,6 +392,7 @@ AC_SUBST(PKG_MAINTAINER)
 AC_SUBST(enable_cxx_exceptions)
 AC_SUBST(enable_debug_frame)
 AC_SUBST(DLLIB)
+AC_SUBST(BACKTRACELIB)
 
 AC_PATH_PROG([LATEX2MAN],[latex2man])
 if test "x$LATEX2MAN" = "x"; then
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 0a74881a..cd3e589b 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -179,7 +179,7 @@ Gtest_bt_LDADD = $(LIBUNWIND) $(LIBUNWIND_local)
 Gtest_concurrent_LDADD = $(LIBUNWIND) $(LIBUNWIND_local) -lpthread
 Gtest_dyn1_LDADD = $(LIBUNWIND) $(LIBUNWIND_local)
 Gtest_exc_LDADD = $(LIBUNWIND) $(LIBUNWIND_local)
-Gtest_init_LDADD = $(LIBUNWIND) $(LIBUNWIND_local)
+Gtest_init_LDADD = $(LIBUNWIND) $(LIBUNWIND_local) @BACKTRACELIB@
 Gtest_resume_sig_LDADD = $(LIBUNWIND) $(LIBUNWIND_local)
 Gtest_resume_sig_rt_LDADD = $(LIBUNWIND) $(LIBUNWIND_local)
 Gperf_simple_LDADD = $(LIBUNWIND) $(LIBUNWIND_local)
@@ -203,7 +203,7 @@ test_setjmp_LDADD = $(LIBUNWIND_setjmp)
 ia64_test_setjmp_LDADD = $(LIBUNWIND_setjmp)
 
 if BUILD_COREDUMP
-test_coredump_unwind_LDADD = $(LIBUNWIND_coredump) $(LIBUNWIND)
+test_coredump_unwind_LDADD = $(LIBUNWIND_coredump) $(LIBUNWIND) @BACKTRACELIB@
 endif
 
 Gia64_test_nat_LDADD = $(LIBUNWIND) $(LIBUNWIND_local)