[MachOYAML] Simplify the section data emitting function. NFC.

[Higuoxing]

Summary

This patch helps simplify some codes in writeSectionData() function.

[jhenderson]

Looks fine. I'm slightly nervous by the hard-coded 16 for the section name max length, but it's probably okay for now, and is no worse than what was there before.

[grimar]

In D85821#2212674, @jhenderson wrote:

Looks fine. I'm slightly nervous by the hard-coded 16 for the section name max length, but it's probably okay for now, and is no worse than what was there before.

Why don't we use something like
assert(sizeof(segname) == 16), or a static assert for segname, or strncmp(&Sec.segname[0], "__DWARF", sizeof(segname)))?

[Higuoxing]

Use sizeof() operator to get rid of hardcoded length.

[grimar]

LGTM

llvm/lib/ObjectYAML/MachOEmitter.cpp

case MachO::LC_SEGMENT_64:
         ZeroToOffset(OS, Sec.offset);
         // Zero Fill any data between the end of the last thing we wrote and the
         // start of this section.
         if (OS.tell() - fileStart > Sec.offset && Sec.offset != (uint32_t)0)
           return createStringError(
               errc::invalid_argument,
               "wrote too much data somewhere, section offsets don't line up");
         if (0 == strncmp(&Sec.segname[0], "__DWARF", 16)) {
-          Error Err = Error::success();
-          cantFail(std::move(Err));
-
-          if (0 == strncmp(&Sec.sectname[0], "__debug_str", 16))
-            Err = DWARFYAML::emitDebugStr(OS, Obj.DWARF);
-          else if (0 == strncmp(&Sec.sectname[0], "__debug_abbrev", 16))
-            Err = DWARFYAML::emitDebugAbbrev(OS, Obj.DWARF);
-          else if (0 == strncmp(&Sec.sectname[0], "__debug_aranges", 16)) {
-            if (Obj.DWARF.DebugAranges)
-              Err = DWARFYAML::emitDebugAranges(OS, Obj.DWARF);
-          } else if (0 == strncmp(&Sec.sectname[0], "__debug_ranges", 16))
-            Err = DWARFYAML::emitDebugRanges(OS, Obj.DWARF);
-          else if (0 == strncmp(&Sec.sectname[0], "__debug_pubnames", 16)) {
-            if (Obj.DWARF.PubNames)
-              Err = DWARFYAML::emitDebugPubnames(OS, Obj.DWARF);
-          } else if (0 == strncmp(&Sec.sectname[0], "__debug_pubtypes", 16)) {
-            if (Obj.DWARF.PubTypes)
-              Err = DWARFYAML::emitDebugPubtypes(OS, Obj.DWARF);
-          } else if (0 == strncmp(&Sec.sectname[0], "__debug_info", 16))
-            Err = DWARFYAML::emitDebugInfo(OS, Obj.DWARF);
-          else if (0 == strncmp(&Sec.sectname[0], "__debug_line", 16))
-            Err = DWARFYAML::emitDebugLine(OS, Obj.DWARF);
-
-          if (Err)
+          StringRef SectName(Sec.sectname, strnlen(Sec.sectname, 16));
+          auto EmitFunc = DWARFYAML::getDWARFEmitterByName(SectName.substr(2));
+          if (Obj.DWARF.getNonEmptySectionNames().count(SectName.substr(2))) {
+            if (Error Err = EmitFunc(OS, Obj.DWARF))
               return Err;
+          }
 
           continue;
         }
 
         // Skip if it's a virtual section.
         if (MachO::isVirtualSection(Sec.flags & MachO::SECTION_TYPE))
           continue;