Prefer libunwind to libbacktrace

configure

@@ -368,14 +368,28 @@ except:
     print("No startup notification support.")
 
 # Add library dependencies detected with using successful compilation test
+bt = False
+if not bt:
+    try:
+        lib, cf, lf = pkg_config('libunwind')
+        LIBS += lib
+        CFLAGS += cf + ['-DHAS_LIBUNWIND']
+        LFLAGS += lf
+        bt = True
+        print("Backtrace support via libunwind.")
+    except:
+        print("No backtrace support via libunwind.")
+if not bt:
     if check_c_compiles([CC, '-lbacktrace'], '''#include <backtrace.h>
             int main() {
                 return 0;
             }'''):
         CFLAGS += ['-DHAS_BACKTRACE']
         LIBS += ['-lbacktrace']
+        bt = True
+        print("Backtrace support via libbacktrace.")
     else:
-    print("No libbacktrace support.")
+        print("No backtrace support via libbacktrace.")
 
 # Add option-dependent flags
 if not args.debug:
@@ -434,6 +448,7 @@ tint2.sources = ['src/config.c',
                  'src/separator/separator.c',
                  'src/tint2rc.c',
                  'src/util/area.c',
+                 'src/util/bt.c',
                  'src/util/common.c',
                  'src/util/fps_distribution.c',
                  'src/util/strnatcmp.c',
@@ -497,7 +512,8 @@ tint2conf.cflags += ['-DTINT2CONF',
                      '-DGETTEXT_PACKAGE=\\"tint2conf\\"',
                      '-DHAVE_VERSION_H']
 
-tint2conf.sources = ['src/util/common.c',
+tint2conf.sources = ['src/util/bt.c',
+                     'src/util/common.c',
                      'src/util/strnatcmp.c',
                      'src/util/cache.c',
                      'src/util/timer.c',

src/util/bt.c

@@ -0,0 +1,264 @@
+/**************************************************************************
+*
+* Tint2 : backtrace
+*
+* Copyright (C) 2007 Pål Staurland (staura@gmail.com)
+* Modified (C) 2008 thierry lorthiois (lorthiois@bbsoft.fr) from Omega distribution
+*
+* This program is free software; you can redistribute it and/or
+* modify it under the terms of the GNU General Public License version 2
+* as published by the Free Software Foundation.
+*
+* This program is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU General Public License for more details.
+* You should have received a copy of the GNU General Public License
+* along with this program; if not, write to the Free Software
+* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+**************************************************************************/
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <stdio.h>
+
+#include "bt.h"
+#include "bool.h"
+
+static void bt_add_frame(struct backtrace *bt, const char *fname)
+{
+    if (bt->frame_count >= BT_MAX_FRAMES)
+        return;
+    struct backtrace_frame *frame = &bt->frames[bt->frame_count];
+    if (fname && *fname) {
+        strncpy(frame->name, fname, BT_FRAME_SIZE);
+    } else {
+        strncpy(frame->name, "??", BT_FRAME_SIZE);
+    }
+    bt->frame_count++;
+}
+
+#ifdef HAS_BACKTRACE
+
+#include <backtrace.h>
+
+static const char *get_exe()
+{
+    static char buf[256] = {0};
+    ssize_t ret = readlink("/proc/self/exe", buf, sizeof(buf)-1);
+    if (ret > 0)
+        return buf;
+    ret = readlink("/proc/curproc/file", buf, sizeof(buf)-1);
+    if (ret > 0)
+        return buf;
+    return buf;
+}
+
+static void bt_error_callback(void *data, const char *msg, int errnum)
+{
+}
+
+static int bt_full_callback(void *data, uintptr_t pc,
+                     const char *filename, int lineno,
+                     const char *function)
+{
+    struct backtrace *bt = (struct backtrace *)data;
+    bt_add_frame(bt, function);
+    return 0;
+}
+
+void get_backtrace(struct backtrace *bt, int skip)
+{
+    static struct backtrace_state *state = NULL;
+
+    if (!state) {
+        const char *exe = get_exe();
+        if (exe)
+            state = backtrace_create_state(exe, 1, bt_error_callback, NULL);
+    }
+    bzero(bt, sizeof(*bt));
+    if (state) {
+        backtrace_full(state, skip + 1, bt_full_callback, bt_error_callback, bt);
+    }
+}
+
+#elif HAS_LIBUNWIND
+
+#define UNW_LOCAL_ONLY
+#include <libunwind.h>
+
+struct bt_mapping {
+    unw_word_t ip;
+    char fname[BT_FRAME_SIZE];
+};
+
+#define BT_BUCKET_SIZE 3
+struct bt_bucket {
+    struct bt_mapping mappings[BT_BUCKET_SIZE];
+};
+
+struct bt_cache {
+    struct bt_bucket *buckets;
+    size_t count;
+    size_t size;
+};
+
+static unsigned oat_hash(void *key, int len)
+{
+    unsigned char *p = key;
+    unsigned h = 0;
+    int i;
+
+    for (i = 0; i < len; i++)
+    {
+        h += p[i];
+        h += (h << 10);
+        h ^= (h >> 6);
+    }
+
+    h += (h << 3);
+    h ^= (h >> 11);
+    h += (h << 15);
+
+    return h;
+}
+
+static struct bt_bucket *cached_proc_name_bucket(struct bt_cache *cache, unw_word_t ip)
+{
+    if (!cache->size)
+        return NULL;
+    unsigned h = oat_hash(&ip, sizeof(ip));
+    return &cache->buckets[h % cache->size];
+}
+
+static void bt_cache_init(struct bt_cache *cache)
+{
+    if (!cache->size) {
+        cache->size = 119;
+        cache->buckets = calloc(cache->size, sizeof(*cache->buckets));
+        if (!cache->buckets)
+            cache->size = 0;
+        cache->count = 0;
+    }
+}
+
+static void cached_proc_name_store(struct bt_cache *cache, unw_word_t ip, const char *fname);
+
+static void bt_cache_rebalance(struct bt_cache *cache)
+{
+    struct bt_cache bigger = {};
+    bigger.size = cache->size * 2 + 1337;
+    bigger.buckets = calloc(bigger.size, sizeof(*bigger.buckets));
+    bigger.count = 0;
+    for (size_t b = 0; b < cache->size; b++) {
+        for (size_t i = 0; i < BT_BUCKET_SIZE; i++) {
+            struct bt_mapping *map = &cache->buckets[b].mappings[i];
+            if (map->ip) {
+                cached_proc_name_store(&bigger, map->ip, map->fname);
+            }
+        }
+    }
+    free(cache->buckets);
+    *cache = bigger;
+}
+
+static void cached_proc_name_store(struct bt_cache *cache, unw_word_t ip, const char *fname)
+{
+    bt_cache_init(cache);
+    if (!cache->size)
+        return;
+    struct bt_bucket *bucket = cached_proc_name_bucket(cache, ip);
+    bool stored = false;
+    for (size_t i = 0; i < BT_BUCKET_SIZE; i++) {
+        if (bucket->mappings[i].ip == ip)
+            return;
+        if (bucket->mappings[i].ip != 0)
+            continue;
+        bucket->mappings[i].ip = ip;
+        strncpy(bucket->mappings[i].fname, fname, sizeof(bucket->mappings[i].fname));
+        cache->count++;
+        stored = true;
+        break;
+    }
+    if (cache->count > cache->size / 4 || !stored) {
+        bt_cache_rebalance(cache);
+        fprintf(stderr, "tint2: proc_name cache: ratio %f, count %lu, size %lu, (%lu bytes)\n",
+                cache->count / (double)cache->size,
+                cache->count, (size_t)cache->size, cache->size * sizeof(*cache->buckets));
+    }
+}
+
+const char *cached_proc_name_get(struct bt_cache *cache, unw_word_t ip)
+{
+    struct bt_bucket *bucket = cached_proc_name_bucket(cache, ip);
+    if (!bucket)
+        return NULL;
+    for (size_t i = 0; i < BT_BUCKET_SIZE; i++) {
+        if (bucket->mappings[i].ip != ip)
+            continue;
+        return bucket->mappings[i].fname;
+    }
+    return NULL;
+}
+
+void get_backtrace(struct backtrace *bt, int skip)
+{
+    static struct bt_cache bt_cache = {};
+    bzero(bt, sizeof(*bt));
+
+    unw_cursor_t cursor;
+    unw_context_t context;
+    unw_getcontext(&context);
+    unw_init_local(&cursor, &context);
+
+    while (unw_step(&cursor) > 0) {
+        if (skip > 0) {
+            skip--;
+            continue;
+        }
+        unw_word_t offset;
+        char fname[BT_FRAME_SIZE] = {0};
+        unw_word_t ip;
+        unw_get_reg(&cursor, UNW_REG_IP, &ip);
+        const char *fname_cached = cached_proc_name_get(&bt_cache, ip);
+        if (fname_cached) {
+            bt_add_frame(bt, fname_cached);
+        } else {
+            unw_get_proc_name(&cursor, fname, sizeof(fname), &offset);
+            cached_proc_name_store(&bt_cache, ip, fname);
+            bt_add_frame(bt, fname);
+        }
+    }
+}
+
+#elif HAS_EXECINFO
+
+#include <execinfo.h>
+
+void get_backtrace(struct backtrace *bt, int skip)
+{
+    bzero(bt, sizeof(*bt));
+
+    void *array[BT_MAX_FRAMES];
+    int size = backtrace(array, BT_MAX_FRAMES);
+    char **strings = backtrace_symbols(array, size);
+
+    for (int i = 0; i < size; i++) {
+        bt_add_frame(bt, strings[i]);
+    }
+
+    free(strings);
+}
+
+
+#else
+
+void get_backtrace(struct backtrace *bt, int skip)
+{
+    bzero(bt, sizeof(*bt));
+}
+
+#endif

src/util/bt.h

@@ -0,0 +1,20 @@
+#ifndef BT_H
+#define BT_H
+
+#include <sys/types.h>
+
+#define BT_FRAME_SIZE 64
+#define BT_MAX_FRAMES 64
+
+struct backtrace_frame {
+    char name[BT_FRAME_SIZE];
+};
+
+struct backtrace {
+    struct backtrace_frame frames[BT_MAX_FRAMES];
+    size_t frame_count;
+};
+
+void get_backtrace(struct backtrace *bt, int skip);
+
+#endif // BT_H

src/util/common.c

@@ -48,18 +48,10 @@
 #include <librsvg/rsvg.h>
 #endif
 
-#ifdef ENABLE_LIBUNWIND
-#define UNW_LOCAL_ONLY
-#include <libunwind.h>
-#else
-#ifdef ENABLE_EXECINFO
-#include <execinfo.h>
-#endif
-#endif
-
 #include "../panel.h"
 #include "timer.h"
 #include "signals.h"
+#include "bt.h"
 
 void write_string(int fd, const char *s)
 {
@@ -83,39 +75,13 @@ void log_string(int fd, const char *s)
 
 void dump_backtrace(int log_fd)
 {
-#ifndef DISABLE_BACKTRACE
+    struct backtrace bt;
+    get_backtrace(&bt, 1);
     log_string(log_fd, "\n" YELLOW "Backtrace:" RESET "\n");
-
+    for (size_t i = 0; i < bt.frame_count; i++) {
-#ifdef ENABLE_LIBUNWIND
+        log_string(log_fd, bt.frames[i].name);
-    unw_cursor_t cursor;
-    unw_context_t context;
-    unw_getcontext(&context);
-    unw_init_local(&cursor, &context);
-
-    while (unw_step(&cursor) > 0) {
-        unw_word_t offset;
-        char fname[128];
-        fname[0] = '\0';
-        (void)unw_get_proc_name(&cursor, fname, sizeof(fname), &offset);
-        log_string(log_fd, fname);
         log_string(log_fd, "\n");
     }
-#else
-#ifdef ENABLE_EXECINFO
-#define MAX_TRACE_SIZE 128
-    void *array[MAX_TRACE_SIZE];
-    size_t size = backtrace(array, MAX_TRACE_SIZE);
-    char **strings = backtrace_symbols(array, size);
-
-    for (size_t i = 0; i < size; i++) {
-        log_string(log_fd, strings[i]);
-        log_string(log_fd, "\n");
-    }
-
-    free(strings);
-#endif // ENABLE_EXECINFO
-#endif // ENABLE_LIBUNWIND
-#endif // DISABLE_BACKTRACE
 }
 
 // sleep() returns early when signals arrive. This function does not.