[llvm-tapi] Don't try to override SequenceTraits for std::string

[sbc100]

Summary

For some reason this doesn't seem to work with LLVM_LINK_LLVM_DYLIB
build.

See https://logs.chromium.org/logs/chromium/bb/client.wasm.llvm/linux/37764/+/recipes/steps/LLVM_regression_tests/0/stdout

What is more it seems that overriding these traits for core types
(including std::string) is not supported/recommend by YAMLTraits.h.
See line 1918 which has the assertion:
"only use LLVM_YAML_IS_SEQUENCE_VECTOR for types you control"

[amontanez]

Apologies, I'll keep a closer eye on that in the future. This can be resolve by doing what ELFArch has done. This requires adding a typedef to TBEHandler.h, changing the declaration of NeededLibs to use the new typedef, and then modifying the ELFYAMLTest.cpp to use something like

LLVM_YAML_STRONG_TYPEDEF(ELFNeededList, ELFNeededMapper)

That should allow us to keep the flow mapping.

[sbc100]

In D55381#1321857, @amontanez wrote:

Apologies, I'll keep a closer eye on that in the future. This can be resolve by doing what ELFArch has done. This requires adding a typedef to TBEHandler.h, changing the declaration of NeededLibs to use the new typedef, and then modifying the ELFYAMLTest.cpp to use something like

LLVM_YAML_STRONG_TYPEDEF(ELFNeededList, ELFNeededMapper)

That should allow us to keep the flow mapping.

Nice! Do you want to do that or should I?

[amontanez]

I can take care of that. I'll add you to the new patch.

[amontanez]

My fix ended up triggering some warnings in the bots that don't really have a reasonable fix so I reverted it. This is probably the best solution for the time being. lgtm

[fedor.sergeev]

In D55381#1322359, @amontanez wrote:

My fix ended up triggering some warnings in the bots that don't really have a reasonable fix so I reverted it. This is probably the best solution for the time being. lgtm

So, whats the plan here?
ElfYamlTextAPI.YAMLWritesNoTBESyms continues to fail in my local builds with LLVM_LINK_LLVM_DYLIB...

[amontanez]

I can open a new patch that does exactly this since this patch is marked as abandoned. I haven't checked to see if phabricator supports re-opening an abandoned change.

[sbc100]

Reopening as the alternative solution had issues.

[amontanez]

No further comments, LGTM

lib/TextAPI/ELF/TBEHandler.cpp

template <> struct CustomMappingTraits<std::set<ELFSymbol>> {
   }
 
   static void output(IO &IO, std::set<ELFSymbol> &Set) {
     for (auto &Sym : Set)
       IO.mapRequired(Sym.Name.c_str(), const_cast<ELFSymbol &>(Sym));
   }
 };
 
-/// YAML traits for generic string vectors (i.e. list of needed libraries).
-template <> struct SequenceTraits<std::vector<std::string>> {
-  static size_t size(IO &IO, std::vector<std::string> &List) {
-    return List.size();
-  }
-
-  static std::string &element(IO &IO, std::vector<std::string> &List,
-                              size_t Index) {
-    if (Index >= List.size())
-      List.resize(Index + 1);
-    return List[Index];
-  }
-
-  // Compacts list of needed libraries into a single line.
-  static const bool flow = true;
-};
-
 /// YAML traits for ELFStub objects.
 template <> struct MappingTraits<ELFStub> {
   static void mapping(IO &IO, ELFStub &Stub) {
     if (!IO.mapTag("!tapi-tbe", true))
       IO.setError("Not a .tbe YAML file.");
     IO.mapRequired("TbeVersion", Stub.TbeVersion);
     IO.mapRequired("SoName", Stub.SoName);
     IO.mapRequired("Arch", (ELFArchMapper &)Stub.Arch);

unittests/TextAPI/ELFYAMLTest.cpp

TEST(ElfYamlTextAPI, YAMLWritesTBESymbols) {
   compareByLine(Result.c_str(), Expected);
 }
 
 TEST(ElfYamlTextAPI, YAMLWritesNoTBESyms) {
   const char Expected[] = "--- !tapi-tbe\n"
                           "TbeVersion:      1.0\n"
                           "SoName:          nosyms.so\n"
                           "Arch:            x86_64\n"
-                          "NeededLibs:      [ libc.so, libfoo.so, libbar.so ]\n"
+                          "NeededLibs:      \n"
+                          "  - libc.so\n"
+                          "  - libfoo.so\n"
+                          "  - libbar.so\n"
                           "Symbols:         {}\n"
                           "...\n";
   ELFStub Stub;
   Stub.TbeVersion = VersionTuple(1, 0);
   Stub.SoName = "nosyms.so";
   Stub.Arch = ELF::EM_X86_64;
   Stub.NeededLibs.push_back("libc.so");
   Stub.NeededLibs.push_back("libfoo.so");