[PATCH] D39550: [ELF] - Fix error reporting with --strip-debug/--strip-all.

[George Rimar via Phabricator via llvm-commits]

grimar created this revision.
Herald added a subscriber: emaste.

Currently LLD tries to use information about functions and variables location
taking it from debug sections. When --strip-* is given we discard such sections
and that breaks error reporting.
Patch stops discarding such sections and delegates handling to `markLive`.


https://reviews.llvm.org/D39550

Files:
  ELF/InputFiles.cpp
  ELF/MarkLive.cpp
  test/ELF/conflict-debug-variable.s


Index: test/ELF/conflict-debug-variable.s
===================================================================
--- test/ELF/conflict-debug-variable.s
+++ test/ELF/conflict-debug-variable.s
@@ -30,6 +30,9 @@
 # CHECK-NEXT: >>> defined at 1.c:1
 # CHECK-NEXT: >>>            {{.*}}:(.bss+0x0)
 
+## Check that stripping debug sections does not break error reporting.
+# RUN: not ld.lld --strip-debug %t.o %t.o -o %t 2>&1 | FileCheck %s
+
 # Used reduced output from following code and gcc 7.1.0
 # to produce this input file:
 # Source (1.c):
Index: ELF/MarkLive.cpp
===================================================================
--- ELF/MarkLive.cpp
+++ ELF/MarkLive.cpp
@@ -255,14 +255,22 @@
     forEachSuccessor<ELFT>(*Q.pop_back_val(), Enqueue);
 }
 
+// Returns true if debug section should be removed from output. Used for
+// implementation of --strip-debug/--strip-all. We can't just discard such
+// sections earlier because may want to use their content for error reporting.
+static bool shouldStrip(InputSectionBase *Sec) {
+  return (Config->Strip != StripPolicy::None) && Sec->Name.startswith(".debug");
+}
+
 // Before calling this function, Live bits are off for all
 // input sections. This function make some or all of them on
 // so that they are emitted to the output file.
 template <class ELFT> void elf::markLive() {
-  // If -gc-sections is missing, no sections are removed.
+  // If -gc-sections is missing, no sections are garbage collected, but we
+  // want to mark debug sections as dead if --strip-debug/--strip-all was used.
   if (!Config->GcSections) {
     for (InputSectionBase *Sec : InputSections)
-      Sec->Live = true;
+      Sec->Live = !shouldStrip(Sec);
     return;
   }
 
@@ -283,7 +291,7 @@
   for (InputSectionBase *Sec : InputSections) {
     bool IsAlloc = (Sec->Flags & SHF_ALLOC);
     bool IsRel = (Sec->Type == SHT_REL || Sec->Type == SHT_RELA);
-    if (!IsAlloc && !IsRel)
+    if (!IsAlloc && !IsRel && !shouldStrip(Sec))
       Sec->Live = true;
   }
 
Index: ELF/InputFiles.cpp
===================================================================
--- ELF/InputFiles.cpp
+++ ELF/InputFiles.cpp
@@ -537,9 +537,6 @@
     return &InputSection::Discarded;
   }
 
-  if (Config->Strip != StripPolicy::None && Name.startswith(".debug"))
-    return &InputSection::Discarded;
-
   // The linkonce feature is a sort of proto-comdat. Some glibc i386 object
   // files contain definitions of symbol "__x86.get_pc_thunk.bx" in linkonce
   // sections. Drop those sections to avoid duplicate symbol errors.


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