libbacktrace patch committed: Don't free strtab if error after reading symbols

[Ian Lance Taylor via Gcc-patches]

This libbacktrace patch fixes the ELF support so that after reading
symbol information we don't free the strtab, even if we encounter an
error later while reading debug info.  This fixes programs that try to
get symbol information even if they can't get backtrace information.
Bootstrapped and ran libbacktrace tests on x86_64-pc-linux-gnu.
Committed to mainline.

Ian

2020-05-09  Ian Lance Taylor  <i...@golang.org>

* elf.c (elf_add): Don't free strtab if an error occurs after
recording symbol information.

index eb481c588e7..1216af86fd9 100644
--- a/libbacktrace/elf.c
+++ b/libbacktrace/elf.c
@@ -3011,6 +3011,7 @@ elf_add (struct backtrace_state *state, const char 
*filename, int descriptor,
         string table permanently.  */
       backtrace_release_view (state, &symtab_view, error_callback, data);
       symtab_view_valid = 0;
+      strtab_view_valid = 0;
 
       *found_sym = 1;