[ELF] - Do not crash when unable to parse ELF object file.

createELFObj() may call error(...), for example when file is too short.
In that case header is not set and following line lead to crash:

EMachine = ELFObj.getHeader()->e_machine;

Patch fixes the issue.

Differential revision: https://reviews.llvm.org/D25233

llvm-svn: 283532

lld/ELF/Error.cpp

@@ -47,4 +47,8 @@ void elf::fatal(const Twine &Msg) {
   exit(1);
 }
 
+void elf::fatal(std::error_code EC, const Twine &Prefix) {
+  fatal(Prefix + ": " + EC.message());
+}
+
 } // namespace lld

lld/ELF/Error.h

@@ -45,6 +45,7 @@ template <typename T> void error(const ErrorOr<T> &V, const Twine &Prefix) {
 }
 
 LLVM_ATTRIBUTE_NORETURN void fatal(const Twine &Msg);
+LLVM_ATTRIBUTE_NORETURN void fatal(std::error_code EC, const Twine &Prefix);
 
 template <class T> T check(ErrorOr<T> E) {
   if (auto EC = E.getError())

lld/ELF/InputFiles.cpp

@@ -57,7 +57,7 @@ template <class ELFT> static ELFFile<ELFT> createELFObj(MemoryBufferRef MB) {
   std::error_code EC;
   ELFFile<ELFT> F(MB.getBuffer(), EC);
   if (EC)
-    error(EC, "failed to read " + MB.getBufferIdentifier());
+    fatal(EC, "failed to read " + MB.getBufferIdentifier());
   return F;
 }
 

lld/test/ELF/invalid/too-short.s

@@ -0,0 +1,5 @@
+# REQUIRES: x86
+
+## too-short.elf file is a truncated ELF.
+# RUN: not ld.lld %S/Inputs/too-short.elf -o %t 2>&1 | FileCheck %s
+# CHECK: failed to read