[PATCH] D54240: [COFF] Improve relocation against discarded section error

[Reid Kleckner via Phabricator via llvm-commits]

rnk created this revision.
rnk added reviewers: ruiu, pcc.

Reuse the "referenced by" note diagnostic code that we already use for
undefined symbols. In my case, it turned this:

  lld-link: error: relocation against symbol in discarded section: .text
  lld-link: error: relocation against symbol in discarded section: .text
  ...

Into this:

  lld-link: error: relocation against symbol in discarded section: .text
  >>> referenced by libANGLE.lib(CompilerGL.obj):(.SCOVP$M)
  >>> referenced by libANGLE.lib(CompilerGL.obj):(.SCOVP$M)
  ...
  
  lld-link: error: relocation against symbol in discarded section: .text
  >>> referenced by obj/third_party/angle/libGLESv2/entry_points_egl_ext.obj:(.SCOVP$M)
  >>> referenced by obj/third_party/angle/libGLESv2/entry_points_egl_ext.obj:(.SCOVP$M)
  ...

I think the new output is more useful.


https://reviews.llvm.org/D54240

Files:
  lld/COFF/Chunks.cpp
  lld/COFF/SymbolTable.cpp
  lld/COFF/SymbolTable.h
  lld/test/COFF/reloc-discarded.s


Index: lld/test/COFF/reloc-discarded.s
===================================================================
--- lld/test/COFF/reloc-discarded.s
+++ lld/test/COFF/reloc-discarded.s
@@ -10,6 +10,7 @@
 # RUN: not lld-link -entry:main -nodefaultlib %t1.obj %t2.obj -out:%t.exe -opt:noref 2>&1 | FileCheck %s
 
 # CHECK: error: relocation against symbol in discarded section: assoc_global
+# CHECK: >>> referenced by {{.*}}reloc-discarded{{.*}}.obj:(main)
 
 	.section	.bss,"bw",discard,main_global
 	.globl	main_global
Index: lld/COFF/SymbolTable.h
===================================================================
--- lld/COFF/SymbolTable.h
+++ lld/COFF/SymbolTable.h
@@ -123,6 +123,8 @@
 
 extern SymbolTable *Symtab;
 
+std::string getSymbolLocations(ObjFile *File, uint32_t SymIndex);
+
 } // namespace coff
 } // namespace lld
 
Index: lld/COFF/SymbolTable.cpp
===================================================================
--- lld/COFF/SymbolTable.cpp
+++ lld/COFF/SymbolTable.cpp
@@ -84,7 +84,7 @@
   return Candidate;
 }
 
-static std::string getSymbolLocations(ObjFile *File, uint32_t SymIndex) {
+std::string lld::coff::getSymbolLocations(ObjFile *File, uint32_t SymIndex) {
   struct Location {
     Symbol *Sym;
     std::pair<StringRef, uint32_t> FileLine;
Index: lld/COFF/Chunks.cpp
===================================================================
--- lld/COFF/Chunks.cpp
+++ lld/COFF/Chunks.cpp
@@ -11,6 +11,7 @@
 #include "InputFiles.h"
 #include "Symbols.h"
 #include "Writer.h"
+#include "SymbolTable.h"
 #include "lld/Common/ErrorHandler.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/BinaryFormat/COFF.h"
@@ -356,7 +357,8 @@
       // with relocations against discarded comdat sections. Such sections
       // are left as is, with relocations untouched.
       if (!Config->MinGW)
-        error("relocation against symbol in discarded section: " + Name);
+        error("relocation against symbol in discarded section: " + Name +
+              getSymbolLocations(File, Rel.SymbolTableIndex));
       continue;
     }
     // Get the output section of the symbol for this relocation.  The output
@@ -374,7 +376,7 @@
       if (isCodeView() || isDWARF())
         continue;
       error("relocation against symbol in discarded section: " +
-            Sym->getName());
+            Sym->getName() + getSymbolLocations(File, Rel.SymbolTableIndex));
       continue;
     }
     uint64_t S = Sym->getRVA();


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