[lld-macho] Demangle location name in undefined symbol diagnostics

[BertalanD]

Summary

If the -demangle flag is passed to lld, symbol names will now be
demangled in the "referenced by:" message in addition to the referenced
symbol's name, which was already demangled before this change.

[thakis]

The patch description is a bit misleading: This already happens for undef diags without debug info, and the patch to look at debug info regressed this for the with-debug-info case and this fixes that regression, right?

[thakis]

(...but with patch description made more precise, lg and thanks!)

[thakis]

(see also lld/test/MachO/demangle.s)

[BertalanD]

This already happens for undef diags without debug info, and the patch to look at debug info regressed this for the with-debug-info case and this fixes that regression, right?

I don't think so. Location messages weren't demangled even before my changes; only the names of the duplicate/undefined symbols were.

[thakis]

Ah I see, it was demangled in the "undefined symbol:" line, but not in the "referenced by:" line. Can you say that in the commit message then? (Ie clarify it only fixes the location message, not the main message, which already worked)

[thakis]

New description looks great. Ship it :)

lld/MachO/InputSection.cpp

if (nextSym == symbols.begin())
     return nullptr;
   return *std::prev(nextSym);
 }
 
 std::string InputSection::getLocation(uint64_t off) const {
   // First, try to find a symbol that's near the offset. Use it as a reference
   // point.
   if (auto *sym = getContainingSymbol(off))
-    return (toString(getFile()) + ":(symbol " + sym->getName() + "+0x" +
+    return (toString(getFile()) + ":(symbol " + toString(*sym) + "+0x" +
             Twine::utohexstr(off - sym->value) + ")")
         .str();
 
   // If that fails, use the section itself as a reference point.
   for (const Subsection &subsec : section.subsections) {
     if (subsec.isec == this) {
       off += subsec.offset;
       break;

lld/test/MachO/invalid/undefined-symbol.s

 # REQUIRES: x86
 # RUN: rm -rf %t; split-file %s %t
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/main.s -o %t/main.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/foo.s -o %t/foo.o
 # RUN: llvm-ar crs %t/foo.a %t/foo.o
 # RUN: not %lld --icf=all -o /dev/null %t/main.o 2>&1 | \
-# RUN:     FileCheck %s -DSYM=_foo -DLOC='%t/main.o:(symbol _main+0x1)'
+# RUN:     FileCheck %s -DSYM=__ZN3foo3barEi -DLOC='%t/main.o:(symbol _main+0x1)'
+# RUN: not %lld -demangle --icf=all -o /dev/null %t/main.o 2>&1 | \
+# RUN:     FileCheck %s -DSYM='foo::bar(int)' -DLOC='%t/main.o:(symbol _main+0x1)'
 # RUN: not %lld -o /dev/null %t/main.o %t/foo.a 2>&1 | \
-# RUN:     FileCheck %s -DSYM=_bar -DLOC='%t/foo.a(foo.o):(symbol _foo+0x1)'
+# RUN:     FileCheck %s -DSYM=_bar -DLOC='%t/foo.a(foo.o):(symbol __ZN3foo3barEi+0x1)'
+# RUN: not %lld -demangle -o /dev/null %t/main.o %t/foo.a 2>&1 | \
+# RUN:     FileCheck %s -DSYM=_bar -DLOC='%t/foo.a(foo.o):(symbol foo::bar(int)+0x1)'
 # RUN: not %lld -o /dev/null %t/main.o -force_load %t/foo.a 2>&1 | \
-# RUN:     FileCheck %s -DSYM=_bar -DLOC='%t/foo.a(foo.o):(symbol _foo+0x1)'
+# RUN:     FileCheck %s -DSYM=_bar -DLOC='%t/foo.a(foo.o):(symbol __ZN3foo3barEi+0x1)'
+# RUN: not %lld -demangle -o /dev/null %t/main.o -force_load %t/foo.a 2>&1 | \
+# RUN:     FileCheck %s -DSYM=_bar -DLOC='%t/foo.a(foo.o):(symbol foo::bar(int)+0x1)'
 # CHECK: error: undefined symbol: [[SYM]]
 # CHECK-NEXT: >>> referenced by [[LOC]]
 
 #--- foo.s
-.globl _foo
+.globl __ZN3foo3barEi
 .text
-_foo:
+__ZN3foo3barEi:
   callq _bar
   retq
 
 #--- main.s
 .text
 
 _anotherref:
-  callq _foo
+  callq __ZN3foo3barEi
   movq $0, %rax
   retq
 
 .globl _main
 _main:
-  callq _foo
+  callq __ZN3foo3barEi
   movq $0, %rax
   retq
 
 .subsections_via_symbols