[obj2yaml] - Report a error when unable to resolve a sh_link reference properly.

Because of a bug we did not report a error in the case
shown in the test. With this patch we do.

Differential revision: https://reviews.llvm.org/D65214

llvm-svn: 367203

llvm/test/tools/obj2yaml/elf-shlink.yaml

@@ -0,0 +1,58 @@
+## Check obj2yaml reports a proper error when unable to resolve
+## a sh_link reference in a regular section.
+## (We had a bug: the error was silently ignored).
+
+# RUN: yaml2obj --docnum=1 %s -o %t1.o
+# RUN: not obj2yaml %t1.o 2>&1 | FileCheck %s -DFILE=%t1.o --check-prefix=ERR1
+
+## ERR1: Error reading file: [[FILE]]: unable to resolve sh_link reference in section '.test': invalid section index: 100
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+Sections:
+  - Name: .test
+    Type: SHT_PROGBITS
+    Link: 100
+
+## Check obj2yaml produce the correct output when a sh_link
+## reference in a regular section can be resolved.
+
+# RUN: yaml2obj --docnum=2 %s -o %t2.o
+# RUN: obj2yaml %t2.o
+# RUN: llvm-readobj -S %t2.o | FileCheck %s --check-prefix=OK
+
+# OK: Name: .test
+# OK: Link:
+# OK-SAME: 1
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+Sections:
+  - Name: .test
+    Type: SHT_PROGBITS
+    Link: 1
+
+## The same as above, but using a section name instead of the numeric value.
+
+# RUN: yaml2obj --docnum=3 %s -o %t3.o
+# RUN: obj2yaml %t3.o
+# RUN: llvm-readobj -S %t3.o | FileCheck %s --check-prefix=OK
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+Sections:
+  - Name: .test
+    Type: SHT_PROGBITS
+    Link: .test

llvm/tools/obj2yaml/elf2yaml.cpp

@@ -376,8 +376,12 @@ Error ELFDumper<ELFT>::dumpCommonSection(const Elf_Shdr *Shdr,
 
   if (Shdr->sh_link != ELF::SHN_UNDEF) {
     auto LinkSection = Obj.getSection(Shdr->sh_link);
-    if (LinkSection.takeError())
-      return LinkSection.takeError();
+    if (!LinkSection)
+      return make_error<StringError>(
+          "unable to resolve sh_link reference in section '" + S.Name +
+              "': " + toString(LinkSection.takeError()),
+          inconvertibleErrorCode());
+
     NameOrErr = getUniquedSectionName(*LinkSection);
     if (!NameOrErr)
       return NameOrErr.takeError();