Revert "X switch to libbacktrace"

This reverts commit 30740602.

libbracktrace is not always automatically installed.

Makefile

@@ -70,8 +70,6 @@ CFLAGS	:= -g -Wall -D_GNU_SOURCE -std=gnu99 -fplan9-extensions	\
 	   -Wno-declaration-after-statement	\
 	   -Wno-error=declaration-after-statement	\
 
-LDLIBS	:= -lbacktrace
-
 # XXX hack ugly
 LOADLIBES=lib/bug.c lib/utils.c 3rdparty/ccan/ccan/tap/tap.c
 TESTS	:= $(patsubst %.c,%,$(wildcard bigfile/tests/test_*.c))
@@ -199,6 +197,7 @@ tfault	:= bigfile/tests/tfault
 FAULTS	:= $(shell grep '{"fault.*"' $(tfault).c | sed 's/"/ /g' |awk '{print $$2}')
 test.fault : $(FAULTS:%=%.tfault)
 
+$(tfault).t: CFLAGS += -rdynamic	# so that backtrace_symbols works
 %.tfault : $(tfault).t
 	t/tfault-run $< $* $(shell grep '{"$*"' $(tfault).c | awk '{print $$NF}')
 

lib/utils.c

@@ -28,8 +28,7 @@
 #include <unistd.h>
 #include <string.h>
 #include <signal.h>
-//#include <execinfo.h>
-#include <backtrace.h>
+#include <execinfo.h>
 
 
 /* ilog2 that must be exact */
@@ -177,32 +176,12 @@ void xwrite(int fd, const void *buf, size_t count)
     }
 }
 
-
-static struct backtrace_state *__backtrace_state;
-
-__attribute__((constructor))
-static void traceback_init(void)
-{
-    __backtrace_state = backtrace_create_state(
-            /*filename*/NULL,
-            /*threaded*/1,
-            /*error callback*/NULL,
-            /*data*/NULL);
-}
-
-
 /* dump traceback to fd */
 void dump_traceback(int fd)
 {
-#if 0
     void *pcv[256];
     int n;
 
-    /* XXX better use https://github.com/ianlancetaylor/libbacktrace
-     * because backtrace_symbols often does not provide symbolic information */
     n = backtrace(pcv, 256);
     backtrace_symbols_fd(pcv, n, fd);
-#else
-    backtrace_print(__backtrace_state, 0, stderr); // XXX use fd instead
-#endif
 }

setup.py

@@ -307,7 +307,6 @@ setup(
                      'lib/utils.c'],
                     depends = libvirtmem_h,
                     define_macros       = [('_GNU_SOURCE',None), ('BUILDING_LIBVIRTMEM',None)],
-                    libraries = ['backtrace'],
                     language = 'c'),
 
                    DSO('wendelin.wcfs.client.libwcfs',