[PATCH] D24731: [GC] Don't crash when printing gc'd sections with no name and no associated file

[Davide Italiano via llvm-commits]

davide updated this revision to Diff 71886.
davide added a comment.

I analyzed this a little bit further.
I think this happen only when we try to print the "special" section `&InputSection<ELFT>::Discarded` (the debugger confirms).
This has no name associated, and I don't think it's backed by a file. I think it's not entirely unreasonable to skip it while reporting sections which have been gc'ed. What do you think?


https://reviews.llvm.org/D24731

Files:
  ELF/Writer.cpp
  test/ELF/lto/dynsym.ll

Index: test/ELF/lto/dynsym.ll
===================================================================
--- test/ELF/lto/dynsym.ll
+++ test/ELF/lto/dynsym.ll
@@ -23,3 +23,8 @@
 define void @foo() {
   ret void
 }
+
+; Check that we don't crash when gc'ing sections and printing the result.
+; RUN: ld.lld -m elf_x86_64 %t2.o %t.so --gc-sections --print-gc-sections \
+; RUN:   -o %t
+; RUN: llvm-readobj -dyn-symbols %t | FileCheck %s
Index: ELF/Writer.cpp
===================================================================
--- ELF/Writer.cpp
+++ ELF/Writer.cpp
@@ -99,7 +99,8 @@
 }

 template <class ELFT> void elf::reportDiscarded(InputSectionBase<ELFT> *IS) {
-  if (!Config->PrintGcSections || !IS || IS->Live)
+  if (!Config->PrintGcSections || !IS || IS == &InputSection<ELFT>::Discarded ||
+      IS->Live)
     return;
   errs() << "removing unused section from '" << IS->Name << "' in file '"
          << IS->getFile()->getName() << "'\n";


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