MB-68141: Add cb::backtrace::current

Add a method which returns the current stacktrace as a string
(to simplify the use in various cases)

Change-Id: I47f9528328804a8f4ff888b6ccbf6ef6e5be6120
Reviewed-on: https://review.couchbase.org/c/platform/+/232397
Reviewed-by: Vesko Karaganev <vesko.karaganev@couchbase.com>
Tested-by: Build Bot <build@couchbase.com>

Author: trondn

include/platform/backtrace.h

@@ -12,6 +12,7 @@
 #include <platform/exceptions.h>
 #include <cstdio>
 #include <functional>
+#include <string>
 
 using write_cb_t = void (*)(void*, const char*);
 
@@ -48,4 +49,11 @@ namespace cb::backtrace {
  * handler).
  */
 void initialize();
+
+/**
+ * Get the current backtrace as a string.
+ *
+ * @return a string containing the backtrace
+ */
+[[nodiscard]] std::string current();
 }

src/backtrace.cc

@@ -21,6 +21,10 @@
 #include <execinfo.h> // for backtrace()
 #endif
 
+#if __cpp_lib_stacktrace
+#include <stacktrace>
+#endif
+
 // Maximum number of frames that will be printed.
 #define MAX_FRAMES 50
 
@@ -200,3 +204,24 @@ void cb::backtrace::initialize() {
     }
 #endif
 }
+
+namespace cb::backtrace {
+
+#if __cpp_lib_stacktrace
+[[nodiscard]] std::string current() {
+    return std::to_string(std::stacktrace::current());
+}
+#else
+static void callback(void* ctx, const char* frame) {
+    auto* result = reinterpret_cast<std::string*>(ctx);
+    result->append(frame);
+    result->append("\n");
+}
+
+[[nodiscard]] std::string current() {
+    std::string result;
+    print_backtrace(callback, &result);
+    return result;
+}
+#endif
+} // namespace cb::backtrace

tests/unit_tests/backtrace_test.cc

@@ -104,3 +104,13 @@ TEST(BackTraceTest, PrintBacktraceToBufferMB19580) {
     EXPECT_TRUE(ArrayFilledWith(char(0xee), redzone_1, redzone_sz));
     EXPECT_TRUE(ArrayFilledWith(char(0xee), redzone_2, redzone_sz));
 }
+
+TEST(BackTraceTest, Current) {
+    auto backtrace = cb::backtrace::current();
+#if defined(WIN32) || defined(__APPLE__)
+    // Arg.. our cv don't give us full symbols on g++ builds...
+    EXPECT_TRUE(backtrace.contains("BackTraceTest")) << backtrace;
+#else
+    EXPECT_TRUE(backtrace.contains("platform_unit_test")) << backtrace;
+#endif
+}