compiler-rt/lib/tsan: allow the Go runtime to return multiple stack frames for a single PC

[randall77]

Summary

This fix allows tsan to report stack traces correctly even in the
presence of mid-stack inlining by the Go compiler.

See https://go-review.googlesource.com/c/go/+/195781 for the Go runtime side of this change.

[dvyukov]

Besides the nits, are you sure we reconstruct the list in the right order? :)
Did you test it with the Go counterpart? There is that buildgo.sh script that builds new syso file, which you can copy into Go runtime/race.
It would also be nice to have an output test for inlined frames here:
https://github.com/golang/go/blob/master/src/runtime/race/output_test.go
It needs to go with the updated syso files, but you could use it for testing now.
Fingers crossed nothing broke since last syso update.

lib/tsan/go/tsan_go.cpp

59

space before (
and generally do for (;;) for this, at least in tsan code

64

no {} around 1-statement blocks

73

no {} around 1-statement blocks

[randall77]

Yes, I tested that frames end up in the right order.
(The list returned by SymbolizeCode needs to go from deepest to shallowest.)

I will work on some tests on the Go side.

[randall77]

Fix Dmitry's comments

[randall77]

Upload right patch this time.

[dvyukov]

Perfect!
Submitted in http://llvm.org/viewvc/llvm-project?view=revision&revision=372205

lib/tsan/go/tsan_go.cpp

struct SymbolizeCodeContext {
   char *func;
   char *file;
   uptr line;
   uptr off;
   uptr res;
 };
 
 SymbolizedStack *SymbolizeCode(uptr addr) {
-  SymbolizedStack *s = SymbolizedStack::New(addr);
+  SymbolizedStack *first = SymbolizedStack::New(addr);
+  SymbolizedStack *s = first;
+  for (;;) {
     SymbolizeCodeContext cbctx;
     internal_memset(&cbctx, 0, sizeof(cbctx));
     cbctx.pc = addr;
     go_runtime_cb(CallbackSymbolizeCode, &cbctx);
-  if (cbctx.res) {
+    if (cbctx.res == 0)
+      break;
     AddressInfo &info = s->info;
     info.module_offset = cbctx.off;
     info.function = internal_strdup(cbctx.func ? cbctx.func : "??");
     info.file = internal_strdup(cbctx.file ? cbctx.file : "-");
     info.line = cbctx.line;
     info.column = 0;
+
+    if (cbctx.pc == addr) // outermost (non-inlined) function
+      break;
+    addr = cbctx.pc;
+    // Allocate a stack entry for the parent of the inlined function.
+    SymbolizedStack *s2 = SymbolizedStack::New(addr);
+    s->next = s2;
+    s = s2;
   }
-  return s;
+  return first;
 }
 
 struct SymbolizeDataContext {
   uptr addr;
   uptr heap;
   uptr start;
   uptr size;
   char *name;