[PATCH] D88715: [llvm-objdump] --source: drop the warning when there is no debug info

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: dblaikie, jhenderson, mmpozulp, rupprecht.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.
MaskRay requested review of this revision.

Warnings have been added for three cases (PR41905): (1) missing debug info, (2)
the source file cannot be found, (3) the debug info points at a line beyond the
end of the file.

(1) is probably less useful. This was brought up once on
http://lists.llvm.org/pipermail/llvm-dev/2020-April/141264.html and an internal
user mentioned it to me that it was annoying. (I personally ignore the warning.)

Users specify --source to get additional information if sources happen to be
available.  If sources are not available, it should be obvious as the output
will have no interleaved source lines. The warning can be especially annoying
when using llvm-objdump -S on a bunch of files.

This patch drops the warning when there is no debug info.
(If LLVMSymbolizer::symbolizeCode returns an `Error`, there will still be
an error. There is currently no test for an `Error` return value.
The only code path is probably a broken symbol table, but we probably already emit a warning
in that case)


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D88715

Files:
  llvm/test/tools/llvm-objdump/X86/source-interleave-no-debug-info.test
  llvm/tools/llvm-objdump/llvm-objdump.cpp


Index: llvm/tools/llvm-objdump/llvm-objdump.cpp
===================================================================
--- llvm/tools/llvm-objdump/llvm-objdump.cpp
+++ llvm/tools/llvm-objdump/llvm-objdump.cpp
@@ -942,8 +942,6 @@
   std::unordered_map<std::string, std::vector<StringRef>> LineCache;
   // Keep track of missing sources.
   StringSet<> MissingSources;
-  // Only emit 'no debug info' warning once.
-  bool WarnedNoDebugInfo;
 
 private:
   bool cacheSource(const DILineInfo& LineInfoFile);
@@ -957,8 +955,7 @@
 
 public:
   SourcePrinter() = default;
-  SourcePrinter(const ObjectFile *Obj, StringRef DefaultArch)
-      : Obj(Obj), WarnedNoDebugInfo(false) {
+  SourcePrinter(const ObjectFile *Obj, StringRef DefaultArch) : Obj(Obj) {
     symbolize::LLVMSymbolizer::Options SymbolizerOpts;
     SymbolizerOpts.PrintFunctions =
         DILineInfoSpecifier::FunctionNameKind::LinkageName;
@@ -1015,20 +1012,13 @@
   DILineInfo LineInfo = DILineInfo();
   auto ExpectedLineInfo = Symbolizer->symbolizeCode(*Obj, Address);
   std::string ErrorMessage;
-  if (!ExpectedLineInfo)
-    ErrorMessage = toString(ExpectedLineInfo.takeError());
-  else
+  if (ExpectedLineInfo) {
     LineInfo = *ExpectedLineInfo;
-
-  if (LineInfo.FileName == DILineInfo::BadString) {
-    if (!WarnedNoDebugInfo) {
-      std::string Warning =
-          "failed to parse debug information for " + ObjectFilename.str();
-      if (!ErrorMessage.empty())
-        Warning += ": " + ErrorMessage;
-      reportWarning(Warning, ObjectFilename);
-      WarnedNoDebugInfo = true;
-    }
+  } else {
+    std::string Warning = "failed to parse debug information for " +
+                          ObjectFilename.str() +
+                          toString(ExpectedLineInfo.takeError());
+    reportWarning(Warning, ObjectFilename);
   }
 
   if (PrintLines)
Index: llvm/test/tools/llvm-objdump/X86/source-interleave-no-debug-info.test
===================================================================
--- llvm/test/tools/llvm-objdump/X86/source-interleave-no-debug-info.test
+++ llvm/test/tools/llvm-objdump/X86/source-interleave-no-debug-info.test
@@ -1,5 +1,5 @@
 ## Test that if an object has no debug information, only the disassembly is
-## printed when --source is specified, and that we emit a warning.
+## printed when --source is specified, and that we do not emit a warning.
 
 # RUN: sed -e "s,SRC_COMPDIR,%/p/Inputs,g" %p/Inputs/source-interleave.ll > %t.ll
 # RUN: llc -o %t.o -filetype=obj -mtriple=x86_64-pc-linux %t.ll
@@ -7,9 +7,8 @@
 
 # RUN: llvm-objdump --source %t.o | FileCheck %s --check-prefixes=CHECK,SOURCE
 # RUN: llvm-objdump --source %t2.o 2> %t2.e | FileCheck %s --check-prefixes=CHECK --implicit-check-not='main()'
-# RUN: FileCheck %s --input-file %t2.e --check-prefixes=WARN
+# RUN: count 0 < %t2.e
 
-# WARN:        warning: '{{.*}}2.o': failed to parse debug information
 # CHECK:       0000000000000010 <main>:
 # SOURCE-NEXT: ; int main() {
 # CHECK-NEXT:   10:   55                      pushq   %rbp


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