Introduce a legacy copy of GetDebugStackTraceHook API.

PiperOrigin-RevId: 852842182
Change-Id: Iadec9bb2fec60b9962a557f82ac998f3cf8d56fe

absl/debugging/internal/examine_stack.cc

diff --git a/absl/debugging/internal/examine_stack.cc b/absl/debugging/internal/examine_stack.cc
index 3dd6ba1..cc24ebd 100644
--- a/absl/debugging/internal/examine_stack.cc
+++ b/absl/debugging/internal/examine_stack.cc
@@ -149,6 +149,10 @@
   debug_stack_trace_hook = hook;
 }
 
+SymbolizeUrlEmitterLegacy GetDebugStackTraceHookLegacy() {
+  return debug_stack_trace_hook;
+}
+
 SymbolizeUrlEmitter GetDebugStackTraceHook() { return debug_stack_trace_hook; }
 
 // Returns the program counter from signal context, nullptr if

absl/debugging/internal/examine_stack.h

diff --git a/absl/debugging/internal/examine_stack.h b/absl/debugging/internal/examine_stack.h
index 190af87..2094d62 100644
--- a/absl/debugging/internal/examine_stack.h
+++ b/absl/debugging/internal/examine_stack.h
@@ -32,12 +32,19 @@
 // `hook` may be called from a signal handler.
 typedef void (*SymbolizeUrlEmitter)(void* const stack[], int depth,
                                     OutputWriter* writer, void* writer_arg);
+typedef void (*SymbolizeUrlEmitterLegacy)(void* const stack[], int depth,
+                                          OutputWriter* writer,
+                                          void* writer_arg);
 
 // Registration of SymbolizeUrlEmitter for use inside of a signal handler.
 // This is inherently unsafe and must be signal safe code.
 void RegisterDebugStackTraceHook(SymbolizeUrlEmitter hook);
 SymbolizeUrlEmitter GetDebugStackTraceHook();
 
+// Currently exact copy of above. Needed for the 3-CL dance due to
+// TCMallocDebugStackTraceHook dependency on this API.
+SymbolizeUrlEmitterLegacy GetDebugStackTraceHookLegacy();
+
 // Returns the program counter from signal context, or nullptr if
 // unknown. `vuc` is a ucontext_t*. We use void* to avoid the use of
 // ucontext_t on non-POSIX systems.