util: Add unit test for stack backtrace caputure

First test never fails, but exercises the code and is useful for
manual inspection.  Second test exposes the android implementation
bug.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6112>

src/util/meson.build

@@ -289,6 +289,18 @@ if with_tests
      suite : ['util'],
   )
 
+  test(
+    'u_debug_stack',
+    executable(
+      'u_debug_stack_test',
+      files('u_debug_stack_test.cpp'),
+      include_directories : [inc_include, inc_src, inc_mapi, inc_mesa, inc_gallium, inc_gallium_aux],
+      dependencies : [idep_mesautil, idep_gtest],
+      c_args : [c_msvc_compat_args],
+    ),
+     suite : ['util'],
+  )
+
   process_test_exe = executable(
     'process_test',
     files('process_test.c'),

src/util/u_debug_stack_test.cpp

@@ -0,0 +1,111 @@
+/*
+ * Copyright © 2020 Google, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <stdio.h>
+#include <gtest/gtest.h>
+
+#include "util/u_debug_stack.h"
+
+static void __attribute__((noinline))
+func_a(void)
+{
+   struct debug_stack_frame backtrace[16];
+
+   fprintf(stderr, "--- backtrace from func_a:\n");
+   debug_backtrace_capture(backtrace, 0, 16);
+   debug_backtrace_dump(backtrace, 16);
+}
+
+static void __attribute__((noinline))
+func_b(void)
+{
+   struct debug_stack_frame backtrace[16];
+
+   func_a();
+
+   fprintf(stderr, "--- backtrace from func_b:\n");
+   debug_backtrace_capture(backtrace, 0, 16);
+   debug_backtrace_dump(backtrace, 16);
+}
+
+static void __attribute__((noinline))
+func_c(struct debug_stack_frame *frames)
+{
+   debug_backtrace_capture(frames, 0, 16);
+}
+
+TEST(u_debug_stack_test, basics)
+{
+   struct debug_stack_frame backtrace[16];
+   struct debug_stack_frame stored_backtrace[16];
+
+   func_c(stored_backtrace);
+
+   fprintf(stderr, "--- backtrace from main to stderr:\n");
+   debug_backtrace_capture(backtrace, 0, 16);
+   debug_backtrace_print(stderr, backtrace, 16);
+
+   fprintf(stderr, "--- backtrace from main again to debug_printf:\n");
+   debug_backtrace_capture(backtrace, 0, 16);
+   debug_backtrace_dump(backtrace, 16);
+
+   func_a();
+
+   func_b();
+
+   fprintf(stderr, "--- stored backtrace from start of main:\n");
+   debug_backtrace_dump(stored_backtrace, 16);
+}
+
+#if _POSIX_C_SOURCE >= 200809L
+
+TEST(u_debug_stack_test, capture_not_overwritten)
+{
+   struct debug_stack_frame backtrace1[16], backtrace2[16];
+
+   FILE *fp;
+   char *bt1, *bt2;
+   size_t size;
+
+   /* Old android implementation uses one global capture per thread. Test that
+    * we can store multiple captures and that they decode to different
+    * backtraces.
+    */
+
+   func_c(backtrace1);
+   debug_backtrace_capture(backtrace2, 0, 16);
+
+   fp = open_memstream(&bt1, &size);
+   debug_backtrace_print(fp, backtrace1, 16);
+   fclose(fp);
+
+   fp = open_memstream(&bt2, &size);
+   debug_backtrace_print(fp, backtrace2, 16);
+   fclose(fp);
+
+   if (size > 0) {
+      EXPECT_STRNE(bt1, bt2);
+   }
+}
+
+#endif