add symbolizer::getStackTrace to replace detail::getSingletonStackTrace

Summary:
Currently, `getSingletonStackTrace` is in the logically private `detail`
namespace. This adds `symbolizer::getStackTrace` to replace `detail::getSingletonStackTrace`,
and this new location mirrors the existing `symbolizer::getAsyncStackTrace`.

The changes will be done in multiple parts:
- Add the new version
- Modify all internal callers to use the new version
- Delete the old version

Reviewed By: yfeldblum

Differential Revision: D33783972

fbshipit-source-id: 137a1d654aea5a451bb90ca12e1916f91589b0df

folly/experimental/symbolizer/Symbolizer.cpp

@@ -400,6 +400,33 @@ void SafeStackTracePrinter::printStackTrace(bool symbolize) {
   }
 }
 
+std::string getStackTraceStr() {
+#if FOLLY_HAVE_ELF && FOLLY_HAVE_DWARF
+
+  // Get and symbolize stack trace
+  constexpr size_t kMaxStackTraceDepth = 100;
+  FrameArray<kMaxStackTraceDepth> addresses;
+
+  if (!getStackTrace(addresses)) {
+    return "";
+  } else {
+    symbolizer::ElfCache elfCache;
+
+    symbolizer::Symbolizer symbolizer(&elfCache);
+    symbolizer.symbolize(addresses);
+
+    symbolizer::StringSymbolizePrinter printer;
+    printer.println(addresses);
+    return printer.str();
+  }
+
+#else
+
+  return "";
+
+#endif // FOLLY_HAVE_ELF && FOLLY_HAVE_DWARF
+}
+
 std::string getAsyncStackTraceStr() {
 #if FOLLY_HAVE_ELF && FOLLY_HAVE_DWARF
 

folly/experimental/symbolizer/Symbolizer.h

@@ -243,6 +243,15 @@ class SafeStackTracePrinter {
   std::unique_ptr<FrameArray<kMaxStackTraceDepth>> addresses_;
 };
 
+/**
+ * Gets the stack trace for the current thread and returns a string
+ * representation. Convenience function meant for debugging and logging.
+ * Empty string indicates stack trace functionality is not available.
+ *
+ * NOT async-signal-safe.
+ */
+std::string getStackTraceStr();
+
 /**
  * Gets the async stack trace for the current thread and returns a string
  * representation. Convenience function meant for debugging and logging.