re PR sanitizer/77631 (no symbols in backtrace shown by ASan when debug info is split)

	PR sanitizer/77631
	* configure.ac: Check for lstat and readlink.
	* elf.c (lstat, readlink): Provide dummy versions if real versions
	are not available.
	* configure, config.h.in: Rebuild.

From-SVN: r253095

libbacktrace/ChangeLog

+2017-09-22  Ian Lance Taylor  <iant@golang.org>
+
+	PR sanitizer/77631
+	* configure.ac: Check for lstat and readlink.
+	* elf.c (lstat, readlink): Provide dummy versions if real versions
+	are not available.
+	* configure, config.h.in: Rebuild.
+
 2017-09-21  Ian Lance Taylor  <iant@google.com>
 
 	PR go/82284

libbacktrace/config.h.in

@@ -37,9 +37,15 @@
 /* Define if AIX loadquery is available. */
 #undef HAVE_LOADQUERY
 
+/* Define to 1 if you have the `lstat' function. */
+#undef HAVE_LSTAT
+
 /* Define to 1 if you have the <memory.h> header file. */
 #undef HAVE_MEMORY_H
 
+/* Define to 1 if you have the `readlink' function. */
+#undef HAVE_READLINK
+
 /* Define to 1 if you have the <stdint.h> header file. */
 #undef HAVE_STDINT_H
 

libbacktrace/configure

@@ -12708,6 +12708,19 @@ cat >>confdefs.h <<_ACEOF
 #define HAVE_DECL_STRNLEN $ac_have_decl
 _ACEOF
 
+for ac_func in lstat readlink
+do :
+  as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
+ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"
+eval as_val=\$$as_ac_var
+   if test "x$as_val" = x""yes; then :
+  cat >>confdefs.h <<_ACEOF
+#define `$as_echo "HAVE_$ac_func" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+done
+
 
 # Check for getexecname function.
 if test -n "${with_target_subdir}"; then

libbacktrace/configure.ac

@@ -373,6 +373,7 @@ if test "$have_fcntl" = "yes"; then
 fi
 
 AC_CHECK_DECLS(strnlen)
+AC_CHECK_FUNCS(lstat readlink)
 
 # Check for getexecname function.
 if test -n "${with_target_subdir}"; then

libbacktrace/elf.c

@@ -75,6 +75,35 @@ xstrnlen (const char *s, size_t maxlen)
 
 #endif
 
+#ifndef HAVE_LSTAT
+
+/* Dummy version of lstat for systems that don't have it.  */
+
+static int
+xlstat (const char *path ATTRIBUTE_UNUSED, struct stat *st ATTRIBUTE_UNUSED)
+{
+  return -1;
+}
+
+#define lstat xlstat
+
+#endif
+
+#ifndef HAVE_READLINK
+
+/* Dummy version of readlink for systems that don't have it.  */
+
+static ssize_t
+xreadlink (const char *path ATTRIBUTE_UNUSED, char *buf ATTRIBUTE_UNUSED,
+	   size_t bufsz ATTRIBUTE_UNUSED)
+{
+  return -1;
+}
+
+#define readlink xreadlink
+
+#endif
+
 #ifndef HAVE_DL_ITERATE_PHDR
 
 /* Dummy version of dl_iterate_phdr for systems that don't have it.  */