Modify InputSectionBase::getLocation to add section and offset to every location string.

[sfertile]

Summary

The section and offset can be very helpful in diagnosing why an error was emitted and how to remedy it, add them to each source location string in InputSectionBase.

[ruiu]

ELF/InputSection.cpp

291

Remove an extraneous space after =.

310

I think that the idea here is that a function name and an object file name uniquely identifies an error location. A section name and an offset is the last resort if there's no other information we can display.

Did you find it useful to print out a section name and an offset in addition to function name? If so, in what situation?

[sfertile]

ELF/InputSection.cpp

310

The motivation for this change comes from a range-check error message I get from a compiler generated file. Since the compiler adds the filename we get a message that look roughly like this:
test.c:(function foo): relocation R_PPC64_ADDR16_DS out of range: 32808 is not in [-32768, 32767]

The problem is that foo could potentially have dozens of R_PPC64_TOC16_DS relocations. By adding the section and offset I can pinpoint exactly which relocation is overflowing/underflowing immediately. The same benefits holds for the checkAlignment diagnostics.

I agree for some of the error messages the extra info holds no value. For example the diagnostic for split-stack prologue adjust failure is completely characterized by the file and the function. I think I would prefer to keep the extra info even in this case so that the diagnostics are consistent and we don't need to be able to generate 2 slightly different formattings but I don't feel to strongly either way.

[ruiu]

LGTM

ELF/InputSection.cpp

310

I'm fine with extra info as long as you find that is useful. At least that shouldn't hurt anyone. Thank you for the explanation!

ELF/InputSection.cpp

if (Defined *D = dyn_cast<Defined>(B))
           Offset < D->Value + D->Size)
         return D;
   return nullptr;
 }
 
 // Returns a source location string. Used to construct an error message.
 template <class ELFT>
 std::string InputSectionBase::getLocation(uint64_t Offset) {
+  std::string SecAndOffset = (Name + "+0x" + utohexstr(Offset)).str();
+
   // We don't have file for synthetic sections.
   if (getFile<ELFT>() == nullptr)
-    return (Config->OutputFile + ":(" + Name + "+0x" + utohexstr(Offset) + ")")
+    return (Config->OutputFile + ":(" + SecAndOffset + ")")
         .str();
 
   // First check if we can get desired values from debugging information.
   if (Optional<DILineInfo> Info = getFile<ELFT>()->getDILineInfo(this, Offset))
-    return Info->FileName + ":" + std::to_string(Info->Line);
+    return Info->FileName + ":" + std::to_string(Info->Line) + ":(" +
+           SecAndOffset + ")";
 
   // File->SourceFile contains STT_FILE symbol that contains a
   // source file name. If it's missing, we use an object file name.
   std::string SrcFile = getFile<ELFT>()->SourceFile;
   if (SrcFile.empty())
     SrcFile = toString(File);
 
   if (Defined *D = getEnclosingFunction<ELFT>(Offset))
-    return SrcFile + ":(function " + toString(*D) + ")";
+    return SrcFile + ":(function " + toString(*D) + ": " + SecAndOffset + ")";
 
   // If there's no symbol, print out the offset in the section.
-  return (SrcFile + ":(" + Name + "+0x" + utohexstr(Offset) + ")").str();
+  return (SrcFile + ":(" + SecAndOffset + ")");
 }
 
 // This function is intended to be used for constructing an error message.
 // The returned message looks like this:
 //
 //   foo.c:42 (/home/alice/possibly/very/long/path/foo.c:42)
 //
 //  Returns an empty string if there's no way to get line info.

test/ELF/ppc64-split-stack-adjust-overflow.s

 
 # RUN: not ld.lld %t1.o %t2.o -o %t --defsym __morestack=0x10010000 2>&1 | \
 # RUN: FileCheck -check-prefix=OVERFLOW %s
 # RUN: not ld.lld %t1.o %t2.o -o %t --defsym __morestack=0x10010000 \
 # RUN: -split-stack-adjust-size 4097 2>&1 | FileCheck -check-prefix=OVERFLOW %s
 # RUN: ld.lld %t1.o %t2.o -o %t --defsym __morestack=0x10010000 -split-stack-adjust-size 4096
 # RUN: llvm-objdump -d %t | FileCheck %s
 
-# OVERFLOW: error: {{.*}}.o:(function caller): split-stack prologue adjustment overflows
+# OVERFLOW: error: {{.*}}.o:(function caller: .text+0x8): split-stack prologue adjustment overflows
 
         .p2align    2
         .global caller
         .type caller, @function
 caller:
 .Lcaller_gep:
     addis 2, 12, .TOC.-.Lcaller_gep@ha
     addi 2, 2, .TOC.-.Lcaller_gep@l

test/ELF/x86-64-reloc-error2.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 # RUN: not ld.lld --entry=func --gc-sections %t.o -o /dev/null 2>&1 | FileCheck %s
 
 ## Check we are able to find a function symbol that encloses
 ## a given location when reporting error messages.
-# CHECK: {{.*}}.o:(function func): relocation R_X86_64_32S out of range: -281474974609408 is not in [-2147483648, 2147483647]
+# CHECK: {{.*}}.o:(function func: .text.func+0x3): relocation R_X86_64_32S out of range: -281474974609408 is not in [-2147483648, 2147483647]
 
 # This mergeable section will be garbage collected. We had a crash issue in that case. Test it.
 .section .rodata.str1,"aMS",@progbits,1
 .asciz "a"
 
 .section .text.func, "ax", %progbits
 .globl func
 .type func,@function
 func:
   movq $func - 0x1000000000000, %rdx
 .size func, .-func

test/ELF/x86-64-reloc-range-debug-loc.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %S/Inputs/x86-64-reloc-error.s -o %tabs
 # RUN: llvm-mc %s -o %t.o -triple x86_64-pc-linux -filetype=obj
 # RUN: not ld.lld %tabs %t.o -o /dev/null -shared 2>&1 | FileCheck %s
 
 ## Check we are able to report file and location from debug information
 ## when reporting such kind of errors.
-# CHECK: error: test.s:3: relocation R_X86_64_32 out of range: 68719476736 is not in [0, 4294967295]
+# CHECK: error: test.s:3:(.text+0x1): relocation R_X86_64_32 out of range: 68719476736 is not in [0, 4294967295]
 
 .section .text,"ax",@progbits
 foo:
 .file 1 "test.s"
 .loc 1 3
  movl $big, %edx
 
 .section .debug_abbrev,"",@progbits