libgo patch committed: Get missing function names from symbol table

Message ID CAOyqgcVWTzzpY-fQuus7kMENXv9iS_skRaGU_v2jcfgDCzVKuA@mail.gmail.com
State New
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  • libgo patch committed: Get missing function names from symbol table
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Commit Message

Ian Lance Taylor Feb. 8, 2018, 3:37 p.m.
This libgo patch changes the traceback code to get missing function
name from the symbol table.  If we trace back through code that has no
debug info, as when calling through C code compiled with -g0, we won't
have a function name.  Try to fetch the function name using the symbol
table.

Adding the test case revealed that gotest failed to use the gccgo tag
when matching files, so add that.

Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
to mainline.

Ian

Patch

Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE	(revision 257493)
+++ gcc/go/gofrontend/MERGE	(working copy)
@@ -1,4 +1,4 @@ 
-2aa95f1499cf931ef8e95c7958463829276a0f2c
+7e94bac5676afc8188677c98ecb263c78c1a7f8d
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: libgo/go/runtime/crash_gccgo_test.go
===================================================================
--- libgo/go/runtime/crash_gccgo_test.go	(nonexistent)
+++ libgo/go/runtime/crash_gccgo_test.go	(working copy)
@@ -0,0 +1,59 @@ 
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build cgo,gccgo
+
+package runtime_test
+
+import (
+	"bytes"
+	"fmt"
+	"internal/testenv"
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+)
+
+func TestGccgoCrashTraceback(t *testing.T) {
+	t.Parallel()
+	got := runTestProg(t, "testprogcgo", "CrashTracebackGccgo")
+	ok := true
+	for i := 1; i <= 3; i++ {
+		if !strings.Contains(got, fmt.Sprintf("CFunction%d", i)) {
+			t.Errorf("missing C function CFunction%d", i)
+			ok = false
+		}
+	}
+	if !ok {
+		t.Log(got)
+	}
+}
+
+func TestGccgoCrashTracebackNodebug(t *testing.T) {
+	testenv.MustHaveGoBuild(t)
+	if os.Getenv("CC") == "" {
+		t.Skip("no compiler in environment")
+	}
+
+	cc := strings.Fields(os.Getenv("CC"))
+	cc = append(cc, "-x", "c++", "-")
+	out, _ := exec.Command(cc[0], cc[1:]...).CombinedOutput()
+	if bytes.Contains(out, []byte("error trying to exec 'cc1plus'")) {
+		t.Skip("no C++ compiler")
+	}
+	os.Setenv("CXX", os.Getenv("CC"))
+
+	got := runTestProg(t, "testprogcxx", "CrashTracebackNodebug")
+	ok := true
+	for i := 1; i <= 3; i++ {
+		if !strings.Contains(got, fmt.Sprintf("cxxFunction%d", i)) {
+			t.Errorf("missing C++ function cxxFunction%d", i)
+			ok = false
+		}
+	}
+	if !ok {
+		t.Log(got)
+	}
+}
Index: libgo/go/runtime/testdata/testprogcgo/traceback_gccgo.go
===================================================================
--- libgo/go/runtime/testdata/testprogcgo/traceback_gccgo.go	(nonexistent)
+++ libgo/go/runtime/testdata/testprogcgo/traceback_gccgo.go	(working copy)
@@ -0,0 +1,40 @@ 
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build gccgo
+
+package main
+
+// This program will crash.
+// We want the stack trace to include the C functions.
+
+/*
+#cgo CFLAGS: -g -O0
+
+#include <stdint.h>
+
+char *p;
+
+static int CFunction3(void) {
+	*p = 0;
+	return 0;
+}
+
+static int CFunction2(void) {
+	return CFunction3();
+}
+
+static int CFunction1(void) {
+	return CFunction2();
+}
+*/
+import "C"
+
+func init() {
+	register("CrashTracebackGccgo", CrashTracebackGccgo)
+}
+
+func CrashTracebackGccgo() {
+	C.CFunction1()
+}
Index: libgo/go/runtime/testdata/testprogcxx/main.go
===================================================================
--- libgo/go/runtime/testdata/testprogcxx/main.go	(nonexistent)
+++ libgo/go/runtime/testdata/testprogcxx/main.go	(working copy)
@@ -0,0 +1,35 @@ 
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "os"
+
+var cmds = map[string]func(){}
+
+func register(name string, f func()) {
+	if cmds[name] != nil {
+		panic("duplicate registration: " + name)
+	}
+	cmds[name] = f
+}
+
+func registerInit(name string, f func()) {
+	if len(os.Args) >= 2 && os.Args[1] == name {
+		f()
+	}
+}
+
+func main() {
+	if len(os.Args) < 2 {
+		println("usage: " + os.Args[0] + " name-of-test")
+		return
+	}
+	f := cmds[os.Args[1]]
+	if f == nil {
+		println("unknown function: " + os.Args[1])
+		return
+	}
+	f()
+}
Index: libgo/go/runtime/testdata/testprogcxx/traceback.cc
===================================================================
--- libgo/go/runtime/testdata/testprogcxx/traceback.cc	(nonexistent)
+++ libgo/go/runtime/testdata/testprogcxx/traceback.cc	(working copy)
@@ -0,0 +1,19 @@ 
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+char *p;
+
+static int cxxFunction3() {
+	*p = 0;
+	return 0;
+}
+
+static int cxxFunction2() {
+	return cxxFunction3();
+}
+
+extern "C"
+int cxxFunction1() {
+	return cxxFunction2();
+}
Index: libgo/go/runtime/testdata/testprogcxx/traceback.go
===================================================================
--- libgo/go/runtime/testdata/testprogcxx/traceback.go	(nonexistent)
+++ libgo/go/runtime/testdata/testprogcxx/traceback.go	(working copy)
@@ -0,0 +1,24 @@ 
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+// This program will crash.
+// We want the stack trace to include the C++ functions,
+// even though we compile with -g0.
+
+/*
+#cgo CXXFLAGS: -g0 -O0
+
+extern int cxxFunction1(void);
+*/
+import "C"
+
+func init() {
+	register("CrashTracebackNodebug", CrashTracebackNodebug)
+}
+
+func CrashTracebackNodebug() {
+	C.cxxFunction1()
+}
Index: libgo/runtime/go-callers.c
===================================================================
--- libgo/runtime/go-callers.c	(revision 257415)
+++ libgo/runtime/go-callers.c	(working copy)
@@ -143,6 +143,20 @@  callback (void *data, uintptr_t pc, cons
   return arg->index >= arg->max;
 }
 
+/* Syminfo callback.  */
+
+static void
+syminfo_fnname_callback (void *data, uintptr_t pc __attribute__ ((unused)),
+			 const char *symname,
+			 uintptr_t address __attribute__ ((unused)),
+			 uintptr_t size __attribute__ ((unused)))
+{
+  Location* locptr = (Location*) data;
+
+  if (symname != NULL)
+    locptr->function = runtime_gostringnocopy ((const byte *) symname);
+}
+
 /* Error callback.  */
 
 static void
@@ -179,15 +193,17 @@  int32
 runtime_callers (int32 skip, Location *locbuf, int32 m, bool keep_thunks)
 {
   struct callers_data data;
+  struct backtrace_state* state;
+  int32 i;
 
   data.locbuf = locbuf;
   data.skip = skip + 1;
   data.index = 0;
   data.max = m;
   data.keep_thunks = keep_thunks;
+  state = __go_get_backtrace_state ();
   runtime_xadd (&runtime_in_callers, 1);
-  backtrace_full (__go_get_backtrace_state (), 0, callback, error_callback,
-		  &data);
+  backtrace_full (state, 0, callback, error_callback, &data);
   runtime_xadd (&runtime_in_callers, -1);
 
   /* For some reason GCC sometimes loses the name of a thunk function
@@ -204,6 +220,18 @@  runtime_callers (int32 skip, Location *l
       --data.index;
     }
 
+  /* Try to use backtrace_syminfo to fill in any missing function
+     names.  This can happen when tracing through an object which has
+     no debug info; backtrace_syminfo will look at the symbol table to
+     get the name.  This should only happen when tracing through code
+     that is not written in Go and is not part of libgo.  */
+  for (i = 0; i < data.index; ++i)
+    {
+      if (locbuf[i].function.len == 0 && locbuf[i].pc != 0)
+	backtrace_syminfo (state, locbuf[i].pc, syminfo_fnname_callback,
+			   error_callback, &locbuf[i]);
+    }
+
   return data.index;
 }
 
Index: libgo/testsuite/gotest
===================================================================
--- libgo/testsuite/gotest	(revision 257415)
+++ libgo/testsuite/gotest	(working copy)
@@ -348,18 +348,18 @@  x)
 			fi
 			match=false
 			;;
-		    $goos | $goarch | cgo | go1.[0-9])
+		    $goos | $goarch | cgo | gccgo | go1.[0-9])
 			match=true
 			;;
-		    "!"$goos | "!"$goarch | "!cgo" | "!"go1.[0-9])
+		    "!"$goos | "!"$goarch | "!cgo" | "!gccgo" | "!"go1.[0-9])
 			;;
 		    *,*)
 			cmatch=true
 			for ctag in `echo $tag | sed -e 's/,/ /g'`; do
 			    case $ctag in
-			    $goos | $goarch | cgo | go1.[0-9])
+			    $goos | $goarch | cgo | gccgo | go1.[0-9])
 				;;
-			    "!"$goos | "!"$goarch | "!cgo" | "!"go1.[0-9])
+			    "!"$goos | "!"$goarch | "!cgo" | "!gccgo" | "!"go1.[0-9])
 				cmatch=false
 				;;
 			    "!"*)