Fixed: state->fileline_fn could be 0 in libbacktrace in some cases

This lead, among other things, to crashes of the apps built with TSan
enabled. When the app (or, to be exact, TSan) tried to output a
backtrace of a suspicious event, backtrace_pcinfo() was invoked.

At the end it called state->fileline_fn() which should have been set
before. However, it was not always the case. If debug info was missing
from some library used by the app or it was in a format that
libbacktrace did not understand, libbacktrace did not set
state->fileline_fn. The latter remained 0 and that resulted in a
segfault in backtrace_pcinfo().

Should now be fixed. The fix makes sure that the callback is always
initialized.

gcc-4.9.1-libbacktrace-fix-null-callback.patch

@@ -0,0 +1,11 @@
+--- gcc-linaro-4.9-2014.07/libbacktrace/elf.c.orig	2014-03-07 09:07:56.000000000 +0400
++++ gcc-linaro-4.9-2014.07/libbacktrace/elf.c	2014-08-13 12:56:23.285272323 +0400
+@@ -925,7 +925,7 @@
+   int ret;
+   int found_sym;
+   int found_dwarf;
+-  fileline elf_fileline_fn;
++  fileline elf_fileline_fn = elf_nodebug;
+   struct phdr_data pd;
+ 
+   ret = elf_add (state, descriptor, 0, error_callback, data, &elf_fileline_fn,

gcc.spec

@@ -200,7 +200,7 @@ Name:		gcc
 %else
 Name:		gcc%{branch}
 %endif
-Release:	2
+Release:	3
 License:	GPLv3+ and GPLv3+ with exceptions and GPLv2+ with exceptions and LGPLv2+ and BSD
 Group:		Development/C
 Url:		http://gcc.gnu.org/
@@ -253,6 +253,8 @@ Patch12:	gcc-4.8-non-fatal-compare-failure.patch
 Patch13:	Gcc-4.8.2-arm-thumb2-CASE_VECTOR_SHORTEN_MODE.patch
 # Backport from upstream
 Patch14:	gcc-4.9.1-bug61801.patch
+# Fix for fileline_fn callback being NULL in libbacktrace sometimes
+Patch15:	gcc-4.9.1-libbacktrace-fix-null-callback.patch
 
 BuildRequires:	binutils >= 2.20.51.0.2
 BuildRequires:	dejagnu
@@ -2170,6 +2172,7 @@ Static liblsan.
 %patch12 -p1 -b .compare~
 %patch13 -p1 -b .short
 %patch14 -p2 -b .bug61801
+%patch15 -p1 -b .libbacktrace
 
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