[lld] reformat multi-line error messages in source code

[thakis]

Summary

This reformats multi-line error messages to look more alike when
printed and in source code. (It does _not_ modify lld's output, it
just changes how the code looks.)

I think this looks nicer. The drawback is that clang-format insists on putting
the "\n" on its own line. Maybe this not being clang-format-compliant is fine
and the increase in readability is worth it, or maybe the increase in
readability is too small to make up for the annoyance of clang-format not Just
Working. I kind of like how this looks right now, but I can also see the
drawback. Sending this out, and unless everyone thinks this is good, then let's
not land it :) (I'll wait for comments for a week or so.)

Also make an /lldmap warning not use the >>> style since it seems
inappropriate there. No other behavior change.

[int3]

Hm, I'd prefer not to have to see spurious clang-format messages.

It also means that I can't just clang-format -i the entire directory any more. I know there's clang-format-diff, but sometimes cleaning up the whole directory is what's needed...

How about introducing a multilineError function that takes multiple string parameters instead and adds the appropriate \n and >>> bits?

[oontvoo]

In D101072#2710088, @int3 wrote:

Hm, I'd prefer not to have to see spurious clang-format messages.

It also means that I can't just clang-format -i the entire directory any more. I know there's clang-format-diff, but sometimes cleaning up the whole directory is what's needed...

How about introducing a multilineError function that takes multiple string parameters instead and adds the appropriate \n and >>> bits?

+1 my $0.02, I'd personally prefer the code to be in a state where running clang-format in a clean checkout does not change anything.
Otherwise, any change made to such code could potentially lead to spurious formatting changes, which is a bit annoying.

[thakis]

A'ight, thanks for humoring me :)

As-is is pretty good.

lld/COFF/Driver.cpp

   config->mapFile = getMapFile(args, OPT_map, OPT_map_file);
 
   if (config->lldmapFile != "" && config->lldmapFile == config->mapFile) {
-    warn("/lldmap and /map have the same output file '" + config->mapFile +
-         "'.\n>>> ignoring /lldmap");
+    warn("/lldmap and /map have same output '" + config->mapFile +
+         "', ignoring /lldmap");
     config->lldmapFile.clear();
   }
 

lld/COFF/DriverUtils.cpp

     std::string sourceStr = source ? toString(source) : "cmd-line";
     std::string existingStr =
         existing.second ? toString(existing.second) : "cmd-line";
-    fatal("/failifmismatch: mismatch detected for '" + k + "':\n>>> " +
-          existingStr + " has value " + existing.first + "\n>>> " + sourceStr +
-          " has value " + v);
+    fatal("/failifmismatch: mismatch detected for '" + k + "':\n"
+          ">>> " + existingStr + " has value " + existing.first + "\n"
+          ">>> " + sourceStr + " has value " + v);
   }
   config->mustMatch[k] = {v, source};
 }

lld/ELF/EhFrame.cpp

 
 private:
   template <class P> void failOn(const P *loc, const Twine &msg) {
-    fatal("corrupted .eh_frame: " + msg + "\n>>> defined in " +
+    fatal("corrupted .eh_frame: " + msg + "\n"
+          ">>> defined in " +
           isec->getObjMsg((const uint8_t *)loc - isec->data().data()));
   }
 

lld/ELF/InputSection.cpp

           Elf_Shdr_Impl<ELFT> sec =
               CHECK(file->getObj().sections(), file)[secIdx];
           warn("relocation refers to a discarded section: " +
-               CHECK(file->getObj().getSectionName(sec), file) +
-               "\n>>> referenced by " + getObjMsg(p->r_offset));
+               CHECK(file->getObj().getSectionName(sec), file) + "\n"
+               ">>> referenced by " + getObjMsg(p->r_offset));
         }
         p->setSymbolAndType(0, 0, false);
         continue;

lld/ELF/OutputSections.cpp

   } else {
     // Otherwise, check if new type or flags are compatible with existing ones.
     if ((flags ^ isec->flags) & SHF_TLS)
-      error("incompatible section flags for " + name + "\n>>> " + toString(isec) +
-            ": 0x" + utohexstr(isec->flags) + "\n>>> output section " + name +
-            ": 0x" + utohexstr(flags));
+      error("incompatible section flags for " + name + "\n"
+            ">>> " + toString(isec) + ": 0x" + utohexstr(isec->flags) + "\n"
+            ">>> output section " + name + ": 0x" + utohexstr(flags));
 
     if (type != isec->type) {
       if (!canMergeToProgbits(type) || !canMergeToProgbits(isec->type))
-        error("section type mismatch for " + isec->name + "\n>>> " +
-              toString(isec) + ": " +
-              getELFSectionTypeName(config->emachine, isec->type) +
-              "\n>>> output section " + name + ": " +
+        error("section type mismatch for " + isec->name + "\n"
+              ">>> " + toString(isec) + ": " +
+              getELFSectionTypeName(config->emachine, isec->type) + "\n"
+              ">>> output section " + name + ": " +
               getELFSectionTypeName(config->emachine, type));
       type = SHT_PROGBITS;
     }

lld/ELF/Symbols.h

   if (symbolKind != PlaceholderKind && !newSym.isLazy() &&
       (type == STT_TLS) != (newSym.type == STT_TLS) &&
       type != llvm::ELF::STT_NOTYPE)
-    error("TLS attribute mismatch: " + toString(*this) + "\n>>> defined in " +
-          toString(newSym.file) + "\n>>> defined in " + toString(file));
+    error("TLS attribute mismatch: " + toString(*this) + "\n"
+          ">>> defined in " + toString(newSym.file) + "\n"
+          ">>> defined in " + toString(file));
 
   Symbol old = *this;
   memcpy(this, &newSym, newSym.getSymbolSize());

lld/ELF/Symbols.cpp

 
   Defined *d = cast<Defined>(sym);
   if (!d->section || !errSec) {
-    error("duplicate symbol: " + toString(*sym) + "\n>>> defined in " +
-          toString(sym->file) + "\n>>> defined in " + toString(newFile));
+    error("duplicate symbol: " + toString(*sym) + "\n"
+          ">>> defined in " + toString(sym->file) + "\n"
+          ">>> defined in " + toString(newFile));
     return;
   }
 

lld/MachO/Driver.cpp

     // via -u flag twice.
     for (const Symbol *undefined : config->explicitUndefineds) {
       if (isa<Undefined>(undefined)) {
-        error("undefined symbol: " + toString(*undefined) +
-              "\n>>> referenced by flag -u " + toString(*undefined));
+        error("undefined symbol: " + toString(*undefined) + "\n"
+              ">>> referenced by flag -u " + toString(*undefined));
         return false;
       }
     }

       if (const Symbol *sym = symtab->find(cachedName))
         if (isa<Defined>(sym))
           continue;
-      error("undefined symbol " + cachedName.val() +
-            "\n>>> referenced from option -exported_symbol(s_list)");
+      error("undefined symbol " + cachedName.val() + "\n"
+            ">>> referenced from option -exported_symbol(s_list)");
     }
 
     if (target->wordSize == 8)

lld/MachO/SymbolTable.cpp

         return defined;
       }
       if (!defined->isWeakDef())
-        error("duplicate symbol: " + name + "\n>>> defined in " +
-              toString(defined->getFile()) + "\n>>> defined in " +
-              toString(file));
+        error("duplicate symbol: " + name + "\n"
+              ">>> defined in " + toString(defined->getFile()) + "\n"
+              ">>> defined in " + toString(file));
     } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
       overridesWeakDef = !isWeakDef && dysym->isWeakDef();
     }

lld/MachO/SyntheticSections.cpp

 static void validateExportSymbol(const Defined *defined) {
   StringRef symbolName = defined->getName();
   if (defined->privateExtern && config->exportedSymbols.match(symbolName))
-    error("cannot export hidden symbol " + symbolName + "\n>>> defined in " +
-          toString(defined->getFile()));
+    error("cannot export hidden symbol " + symbolName + "\n"
+          ">>> defined in " + toString(defined->getFile()));
 }
 
 static bool shouldExportSymbol(const Defined *defined) {