[lld] r281946 - [GC] Don't crash when printing the special Discarded GC section.

[Davide Italiano via llvm-commits]

Author: davide
Date: Mon Sep 19 18:15:51 2016
New Revision: 281946

URL: http://llvm.org/viewvc/llvm-project?rev=281946&view=rev
Log:
[GC] Don't crash when printing the special Discarded GC section.

InputSection<ELFT>::Discarded has no name and it's not backed by
a file. Trying to report it as discared will cause a nullptr
dereference, therefore a crash. Skip it.

Differential Revision:   https://reviews.llvm.org/D24731

Modified:
    lld/trunk/ELF/Writer.cpp
    lld/trunk/test/ELF/lto/dynsym.ll

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=281946&r1=281945&r2=281946&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Mon Sep 19 18:15:51 2016
@@ -102,7 +102,8 @@ StringRef elf::getOutputSectionName(Inpu
 }
 
 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";

Modified: lld/trunk/test/ELF/lto/dynsym.ll
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/lto/dynsym.ll?rev=281946&r1=281945&r2=281946&view=diff
==============================================================================
--- lld/trunk/test/ELF/lto/dynsym.ll (original)
+++ lld/trunk/test/ELF/lto/dynsym.ll Mon Sep 19 18:15:51 2016
@@ -5,6 +5,11 @@
 ; RUN: ld.lld -m elf_x86_64 %t2.o %t.so -o %t
 ; RUN: llvm-readobj -dyn-symbols %t | FileCheck %s
 
+; 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
+
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"