[lld-macho] -section_rename should work on synthetic sections too

[int3]

Summary

Previously, we only applied the renames to
ConcatOutputSections.

lld/MachO/SyntheticSections.h

 public:
   SyntheticSection(const char *segname, const char *name);
   virtual ~SyntheticSection() = default;
 
   static bool classof(const OutputSection *sec) {
     return sec->kind() == SyntheticKind;
   }
 
-  const StringRef segname;
+  StringRef segname;
   // This fake InputSection makes it easier for us to write code that applies
   // generically to both user inputs and synthetics.
   InputSection *isec;
 };
 
 // All sections in __LINKEDIT should inherit from this.
 class LinkEditSection : public SyntheticSection {
 public:

lld/MachO/SyntheticSections.cpp

 using namespace llvm::support::endian;
 using namespace lld;
 using namespace lld::macho;
 
 InStruct macho::in;
 std::vector<SyntheticSection *> macho::syntheticSections;
 
 SyntheticSection::SyntheticSection(const char *segname, const char *name)
-    : OutputSection(SyntheticKind, name), segname(segname) {
+    : OutputSection(SyntheticKind, name) {
+  std::tie(this->segname, this->name) = maybeRenameSection({segname, name});
   isec = make<ConcatInputSection>(segname, name);
   isec->parent = this;
   syntheticSections.push_back(this);
 }
 
 // dyld3's MachOLoaded::getSlide() assumes that the __TEXT segment starts
 // from the beginning of the file (i.e. the header).
 MachHeaderSection::MachHeaderSection()

lld/MachO/Writer.h

 //===- Writer.h -------------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLD_MACHO_WRITER_H
 #define LLD_MACHO_WRITER_H
 
+#include "Config.h"
+
 #include <cstdint>
 
 namespace lld {
 namespace macho {
 
 class OutputSection;
 class InputSection;
 class Symbol;
 
 class LoadCommand {
 public:
   virtual ~LoadCommand() = default;
   virtual uint32_t getSize() const = 0;
   virtual void writeTo(uint8_t *buf) const = 0;
 };
 
 template <class LP> void writeResult();
 
+NamePair maybeRenameSection(NamePair key);
+
 void createSyntheticSections();
 
 // Add bindings for symbols that need weak or non-lazy bindings.
 void addNonLazyBindingEntries(const Symbol *, const InputSection *,
                               uint64_t offset, int64_t addend = 0);
 
 extern OutputSection *firstTLVDataSection;
 
 } // namespace macho
 } // namespace lld
 
 #endif

lld/MachO/Writer.cpp

for (OutputSection *osec : seg->getSections()) {
                               return isecPriorities[a] > isecPriorities[b];
                             });
         }
       }
     }
   }
 }
 
-static NamePair maybeRenameSection(NamePair key) {
+NamePair macho::maybeRenameSection(NamePair key) {
   auto newNames = config->sectionRenameMap.find(key);
   if (newNames != config->sectionRenameMap.end())
     return newNames->second;
   auto newName = config->segmentRenameMap.find(key.first);
   if (newName != config->segmentRenameMap.end())
     return std::make_pair(newName->second, key.second);
   return key;
 }

lld/test/MachO/rename.s

 # BAD2-DAG: error: invalid name for segment or section: PL+SSY_SEG
 # BAD2-DAG: error: invalid name for segment or section: -o
 # BAD2-DAG: error: {{.*}}: unhandled file type
 
 ## Check that section and segment renames happen
 # RUN: %lld \
 # RUN:     -rename_section __FROM_SECT __from_sect __TO_SECT __to_sect \
 # RUN:     -rename_segment __FROM_SEG __TO_SEG \
+# RUN:     -rename_section __TEXT __cstring __RODATA __cstring \
 # RUN:   -o %t %t.o
 # RUN: llvm-objdump --macho --all-headers %t | FileCheck %s
 
 # CHECK:      {{^}}Section{{$}}
 # CHECK-NEXT: sectname __text
 # CHECK-NEXT: segname __TEXT
 # CHECK:      {{^}}Section{{$}}
-# CHECK-NOT:  sectname __from_sect
 # CHECK-NEXT: sectname __to_sect
-# CHECK-NOT:  segname __FROM_SECT
 # CHECK-NEXT: segname __TO_SECT
 # CHECK:      {{^}}Section{{$}}
 # CHECK-NEXT: sectname __from_seg
-# CHECK-NOT:  segname __FROM_SEG
 # CHECK-NEXT: segname __TO_SEG
+# CHECK:      {{^}}Section{{$}}
+# CHECK-NEXT: sectname __cstring
+# CHECK-NEXT: segname __RODATA
 
 .section __FROM_SECT,__from_sect
 .global _from_sect
 _from_sect:
   .space 8
 
 .section __FROM_SEG,__from_seg
 .global _from_seg
 _from_seg:
   .space 8
 
+## This is a synthetic section; make sure it gets renamed too.
+.cstring
+  .space 8
+
 .text
 .global _main
 _main:
   ret