https://github.com/MaskRay created
https://github.com/llvm/llvm-project/pull/75022
When the main file is preprocessed and we change `MainFileName` to the
original source file name (e.g. `a.i => a.c`), the source manager does
not contain `a.c`, but we incorrectly associate the DIFile(a.c) with
md5(a.i). This causes CGDebugInfo::emitFunctionStart to create a
duplicate DIFile and leads to a spurious "inconsistent use of MD5
checksums" warning.
```
% cat a.c
void f() {}
% clang -c -g a.c # no warning
% clang -E a.c -o a.i && clang -g -S a.i && clang -g -c a.s
a.s:9:2: warning: inconsistent use of MD5 checksums
.file 1 "a.c"
^
% grep DIFile a.ll
!1 = !DIFile(filename: "a.c", directory: "/tmp/c", checksumkind: CSK_MD5,
checksum: "c5b2e246df7d5f53e176b097a0641c3d")
!11 = !DIFile(filename: "a.c", directory: "/tmp/c")
% grep 'file.*a.c' a.s
.file "a.c"
.file 0 "/tmp/c" "a.c" md5 0x2d14ea70fee15102033eb8d899914cce
.file 1 "a.c"
```
Fix #56378 by disassociating md5(a.i) with a.c.
>From ace1e56b3db30466748dc7d8c5ba10ebf4001bd5 Mon Sep 17 00:00:00 2001
From: Fangrui Song <i...@maskray.me>
Date: Sun, 10 Dec 2023 19:18:36 -0800
Subject: [PATCH] [DebugInfo] Fix duplicate DIFile when main file is
preprocessed
When the main file is preprocessed and we change `MainFileName` to the
original source file name (e.g. `a.i => a.c`), the source manager does
not contain `a.c`, but we incorrectly associate the DIFile(a.c) with
md5(a.i). This causes CGDebugInfo::emitFunctionStart to create a
duplicate DIFile and leads to a spurious "inconsistent use of MD5
checksums" warning.
```
% cat a.c
void f() {}
% clang -c -g a.c # no warning
% clang -E a.c -o a.i && clang -g -S a.i && clang -g -c a.s
a.s:9:2: warning: inconsistent use of MD5 checksums
.file 1 "a.c"
^
% grep DIFile a.ll
!1 = !DIFile(filename: "a.c", directory: "/tmp/c", checksumkind: CSK_MD5,
checksum: "c5b2e246df7d5f53e176b097a0641c3d")
!11 = !DIFile(filename: "a.c", directory: "/tmp/c")
% grep 'file.*a.c' a.s
.file "a.c"
.file 0 "/tmp/c" "a.c" md5 0x2d14ea70fee15102033eb8d899914cce
.file 1 "a.c"
```
Fix #56378 by disassociating md5(a.i) with a.c.
---
clang/lib/CodeGen/CGDebugInfo.cpp | 10 ++++++----
clang/test/CodeGen/debug-info-preprocessed-file.i | 4 ++++
2 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp
b/clang/lib/CodeGen/CGDebugInfo.cpp
index 7cf661994a29c..37d7a6755d390 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -554,14 +554,16 @@ void CGDebugInfo::CreateCompileUnit() {
// If the main file name provided is identical to the input file name, and
// if the input file is a preprocessed source, use the module name for
// debug info. The module name comes from the name specified in the first
- // linemarker if the input is a preprocessed source.
+ // linemarker if the input is a preprocessed source. In this case we don't
+ // know the content to compute a checksum.
if (MainFile->getName() == MainFileName &&
FrontendOptions::getInputKindForExtension(
MainFile->getName().rsplit('.').second)
- .isPreprocessed())
+ .isPreprocessed()) {
MainFileName = CGM.getModule().getName().str();
-
- CSKind = computeChecksum(SM.getMainFileID(), Checksum);
+ } else {
+ CSKind = computeChecksum(SM.getMainFileID(), Checksum);
+ }
}
llvm::dwarf::SourceLanguage LangTag;
diff --git a/clang/test/CodeGen/debug-info-preprocessed-file.i
b/clang/test/CodeGen/debug-info-preprocessed-file.i
index 23fd26525e3bf..c8a2307d46c31 100644
--- a/clang/test/CodeGen/debug-info-preprocessed-file.i
+++ b/clang/test/CodeGen/debug-info-preprocessed-file.i
@@ -6,6 +6,10 @@
# 1 "<built-in>" 2
# 1 "preprocessed-input.c" 2
+/// The main file is preprocessed. We change it to preprocessed-input.c. Since
+/// the content is not available, we don't compute a checksum.
// RUN: %clang -g -c -S -emit-llvm -o - %s | FileCheck %s
// CHECK: !DICompileUnit(language: DW_LANG_C{{.*}}, file: ![[FILE:[0-9]+]]
// CHECK: ![[FILE]] = !DIFile(filename: "/foo/bar/preprocessed-input.c"
+// CHECK-NOT: checksumkind:
+// CHECK-NOT: !DIFile(
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