stacktrace_test: avoid spoiling errno in the test signal handler.

PiperOrigin-RevId: 799631809
Change-Id: I456c0721e56a80a09a510c3556d8aace436717a5

Author: Abseil Team

absl/debugging/BUILD.bazel

@@ -69,6 +69,7 @@ cc_test(
         ":stacktrace",
         "//absl/base:config",
         "//absl/base:core_headers",
+        "//absl/base:errno_saver",
         "//absl/types:span",
         "@googletest//:gtest",
         "@googletest//:gtest_main",

absl/debugging/CMakeLists.txt

@@ -58,6 +58,7 @@ absl_cc_test(
     absl::stacktrace
     absl::config
     absl::core_headers
+    absl::errno_saver
     absl::span
     GTest::gmock_main
 )

absl/debugging/stacktrace_test.cc

@@ -27,6 +27,7 @@
 #include "gtest/gtest.h"
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
+#include "absl/base/internal/errno_saver.h"
 #include "absl/base/optimization.h"
 #include "absl/types/span.h"
 
@@ -414,6 +415,7 @@ const void* g_return_address = nullptr;
 bool g_sigusr2_raised = false;
 
 void SigUsr2Handler(int, siginfo_t*, void* uc) {
+  absl::base_internal::ErrnoSaver errno_saver;
   // Many platforms don't support this by default.
   bool support_is_expected = false;
   constexpr int kMaxStackDepth = 64;