[PATCH] D21818: Add artificial debug information to avoid compiler crash

[Yunzhong Gao via llvm-commits]

ygao created this revision.
ygao added reviewers: aprantl, echristo, dblaikie.
ygao added a subscriber: llvm-commits.
Herald added a subscriber: mehdi_amini.

Hi,
The compiler crashed with the following test program:

/* test.c
 * To reproduce:
 * $ clang -c -g -fstack-protector-strong test.c
 * (fatal error: error in backend: Broken function found, compilation aborted!)
 * (need  an assertion-enabled build of the compiler)
 */
void __stack_chk_fail(void) { return; }

void foo() {
  char bar[5];
}
/* end of test.c */

This is not a legitimate input C file because __stack_chk_fail is a reserved function name.
On the other hand, it seems that the compiler should be able to give a nicer diagnostic or
otherwise fail more gracefully instead of having to crash on invalid input (in the spirit of all
"internal compiler error"s are compiler bugs).

The proposed patch here attempts to add artificial debug information when the compiler
generates the call to __stack_chk_fail. Does this look like a reasonable thing to do?

Many thanks in advance,
- Gao

http://reviews.llvm.org/D21818

Files:
  lib/CodeGen/StackProtector.cpp
  test/CodeGen/X86/stack-protector.ll

Index: test/CodeGen/X86/stack-protector.ll
===================================================================
--- test/CodeGen/X86/stack-protector.ll
+++ test/CodeGen/X86/stack-protector.ll
@@ -3880,6 +3880,17 @@
   ret i32 %call
 }
 
+define void @__stack_chk_fail() #1 !dbg !6 {
+entry:
+  ret void
+}
+
+define void @test32() #1 !dbg !7 {
+entry:
+  %0 = alloca [5 x i8], align 1
+  ret void
+}
+
 declare double @testi_aux()
 declare i8* @strcpy(i8*, i8*)
 declare i32 @printf(i8*, ...)
@@ -3899,3 +3910,16 @@
 attributes #3 = { ssp "stack-protector-buffer-size"="33" }
 attributes #4 = { ssp "stack-protector-buffer-size"="5" }
 attributes #5 = { ssp "stack-protector-buffer-size"="6" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+!llvm.ident = !{!5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1)
+!1 = !DIFile(filename: "test.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{!"clang version x.y.z"}
+!6 = distinct !DISubprogram(name: "__stack_chk_fail", scope: !1, unit: !0)
+!7 = distinct !DISubprogram(name: "foo", scope: !1, unit: !0)
Index: lib/CodeGen/StackProtector.cpp
===================================================================
--- lib/CodeGen/StackProtector.cpp
+++ lib/CodeGen/StackProtector.cpp
@@ -25,6 +25,7 @@
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalValue.h"
@@ -448,6 +449,7 @@
   LLVMContext &Context = F->getContext();
   BasicBlock *FailBB = BasicBlock::Create(Context, "CallStackCheckFailBlk", F);
   IRBuilder<> B(FailBB);
+  B.SetCurrentDebugLocation(DebugLoc::get(0, 0, F->getSubprogram()));
   if (Trip.isOSOpenBSD()) {
     Constant *StackChkFail =
         M->getOrInsertFunction("__stack_smash_handler",


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