[PATCH] D80803: [DebugInfo] Add flush to ensure debug line errors are in right place

[James Henderson via Phabricator via llvm-commits]

jhenderson created this revision.
jhenderson added reviewers: JDevlieghere, aprantl, ikudrin, probinson, dblaikie, MaskRay.
Herald added subscribers: cmtice, hiraditya.
Herald added a project: LLVM.

The debug line error messages can end up being printed before the stdout buffer is flushed, meaning they can appear before the header part of the output. Flushing at the start of dumping the line table ensures each table's error messages are in the right

This patch also adds a couple of comments to explain the need for the other flushes in the same area.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D80803

Files:
  llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
  llvm/test/tools/llvm-dwarfdump/X86/debug_line_invalid.test


Index: llvm/test/tools/llvm-dwarfdump/X86/debug_line_invalid.test
===================================================================
--- llvm/test/tools/llvm-dwarfdump/X86/debug_line_invalid.test
+++ llvm/test/tools/llvm-dwarfdump/X86/debug_line_invalid.test
@@ -4,40 +4,43 @@
 ## Show that a bad length stops parsing of the section.
 # RUN: llvm-mc -triple x86_64-pc-linux %S/Inputs/debug_line_reserved_length.s -filetype=obj -o %t-reserved.o
 # RUN: llvm-dwarfdump -debug-line %t-reserved.o 2>&1 \
-# RUN:   | FileCheck %s --check-prefixes=FIRST,FATAL,RESERVED
+# RUN:   | FileCheck %s --check-prefixes=HEADER,FIRST,FATAL,RESERVED
 # RUN: llvm-dwarfdump -debug-line %t-reserved.o -verbose 2>&1 \
-# RUN:   | FileCheck %s --check-prefixes=FIRST,FATAL,RESERVED
+# RUN:   | FileCheck %s --check-prefixes=HEADER,FIRST,FATAL,RESERVED
 
 ## We only produce warnings for malformed tables after the specified unit if
 ## parsing can continue.
 # RUN: llvm-dwarfdump -debug-line=0 %t-reserved.o 2>&1 \
-# RUN:   | FileCheck %s --check-prefixes=FIRST,NOLATER,RESERVED
+# RUN:   | FileCheck %s --check-prefixes=HEADER,FIRST,NOLATER,RESERVED
 
 ## Stop looking for the specified unit, if a fatally-bad prologue is detected.
 # RUN: llvm-dwarfdump -debug-line=0x4b %t-reserved.o 2>&1 \
-# RUN:   | FileCheck %s --check-prefixes=NOFIRST,NOLATER,RESERVED
+# RUN:   | FileCheck %s --check-prefixes=HEADER,NOFIRST,NOLATER,RESERVED
 
 ## Show that non-fatal errors do not prevent parsing the rest of the section.
 # RUN: llvm-mc -triple x86_64-pc-linux %S/Inputs/debug_line_malformed.s -filetype=obj -o %t-malformed.o
 # RUN: llvm-dwarfdump -debug-line %t-malformed.o 2> %t-malformed.err \
-# RUN:   | FileCheck %s --check-prefixes=FIRST,NONFATAL,LAST --implicit-check-not='debug_line[{{.*}}]'
+# RUN:   | FileCheck %s --check-prefixes=HEADER,FIRST,NONFATAL,LAST --implicit-check-not='debug_line[{{.*}}]'
 # RUN: FileCheck %s --input-file=%t-malformed.err --check-prefixes=ALL,OTHER
 # RUN: llvm-dwarfdump -debug-line %t-malformed.o -verbose 2> %t-malformed-verbose.err \
-# RUN:   | FileCheck %s --check-prefixes=FIRST,NONFATAL,LAST --implicit-check-not='debug_line[{{.*}}]'
+# RUN:   | FileCheck %s --check-prefixes=HEADER,FIRST,NONFATAL,LAST --implicit-check-not='debug_line[{{.*}}]'
 # RUN: FileCheck %s --input-file=%t-malformed-verbose.err --check-prefixes=ALL,OTHER
 
 ## We should still produce warnings for malformed tables after the specified unit.
 # RUN: llvm-dwarfdump -debug-line=0 %t-malformed.o 2> %t-malformed-off-first.err \
-# RUN:   | FileCheck %s --check-prefixes=FIRST,NOLATER
+# RUN:   | FileCheck %s --check-prefixes=HEADER,FIRST,NOLATER
 # RUN: FileCheck %s --input-file=%t-malformed-off-first.err --check-prefix=ALL
 
 ## Don't stop looking for the later unit if non-fatal issues are found.
 # RUN: llvm-dwarfdump -debug-line=0x3c9 %t-malformed.o 2> %t-malformed-off-last.err \
-# RUN:   | FileCheck %s --check-prefix=LAST --implicit-check-not='debug_line[{{.*}}]'
+# RUN:   | FileCheck %s --check-prefixes=HEADER,LAST --implicit-check-not='debug_line[{{.*}}]'
 # RUN: FileCheck %s --input-file=%t-malformed-off-last.err --check-prefix=ALL
 
+# HEADER:      .debug_line contents:
+
 # FIRST:       debug_line[0x00000000]
 # FIRST:       0x000000000badbeef {{.*}} end_sequence
+# FIRST-EMPTY:
 # NOFIRST-NOT: debug_line[0x00000000]
 # NOFIRST-NOT: 0x000000000badbeef {{.*}} end_sequence
 # NOLATER-NOT: debug_line[{{.*}}]
@@ -45,8 +48,7 @@
 
 ## For fatal issues, the following table(s) should not be dumped:
 # FATAL:      debug_line[0x00000048]
-# RESERVED-NOT: prologue
-# RESERVED: warning: parsing line table prologue at offset 0x00000048: unsupported reserved unit length of value 0xfffffffe
+# RESERVED-NEXT: warning: parsing line table prologue at offset 0x00000048: unsupported reserved unit length of value 0xfffffffe
 # RESERVED-NOT: prologue
 # FATAL-NOT:  debug_line
 
Index: llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
===================================================================
--- llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
+++ llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
@@ -491,6 +491,9 @@
   auto DumpLineSection = [&](DWARFDebugLine::SectionParser Parser,
                              DIDumpOptions DumpOpts,
                              Optional<uint64_t> DumpOffset) {
+    // Flush immediately to ensure error messages from parsing are printed after
+    // any existing output.
+    OS.flush();
     while (!Parser.done()) {
       if (DumpOffset && Parser.getOffset() != *DumpOffset) {
         Parser.skip(DumpOpts.WarningHandler, DumpOpts.WarningHandler);
@@ -498,6 +501,8 @@
       }
       OS << "debug_line[" << format("0x%8.8" PRIx64, Parser.getOffset())
          << "]\n";
+      // Flush after the table header is printed to ensure error messages for
+      // this table are printed after it.
       OS.flush();
       if (DumpOpts.Verbose) {
         Parser.parseNext(DumpOpts.WarningHandler, DumpOpts.WarningHandler, &OS);
@@ -506,6 +511,8 @@
             Parser.parseNext(DumpOpts.WarningHandler, DumpOpts.WarningHandler);
         LineTable.dump(OS, DumpOpts);
       }
+      // Flush now to ensure later error output does not get mixed in with the
+      // line table output.
       OS.flush();
     }
   };


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