[gold] Handle modules that are not included in the link.

[eugenis]

Summary

Gold has a newly added LDPT_GET_SYMBOLS_V3 callback that can
distinguish between a module that is not included in the link, and
one that is included but has its entire interface preempted by others.

Fixes PR26674.

[eugenis]

I'm not sure how to test this, other than with an explicit check for the gold version.

[• rafael]

tools/gold/gold-plugin.cpp

58

you need a ifndef, no?

278

git-clang-format.

574

Can this ever happen?

[eugenis]

tools/gold/gold-plugin.cpp

58

It's an enum, not a macro. The samewith LDPO_PIE above, we could remove the #ifdef - unless it's meant to be configurable with -DLDPO_PIE or something (but that seems unlikely).

[• rafael]

This formatted more than what I was expecting.

I am OK with this with the ifdef part fixed. Just wait for Teresa to comment on getFunctionIndexForFile.

tools/gold/gold-plugin.cpp

58

They should be consistent. Se either remove the ifdef of LDPO_PIE or add one here.

[eugenis]

Removed ifndef around LDPO_PIE.
I've reformatted the whole function (git-clang-format did not work for me for some reason). It's probably better to have consistent formatting inside a function (if not across the whole file).

[• rafael]

LGTM, but please wait for Teresa to comment on there being any interaction between getFunctionIndexForFile and --start-lib/--end-lib.

[• rafael]

tools/gold/gold-plugin.cpp

920

ah, and git-clang-format this one :-)

[tejohnson]

In D17867#367684, @rafael wrote:

LGTM, but please wait for Teresa to comment on there being any interaction between getFunctionIndexForFile and --start-lib/--end-lib.

LGTM too. I reviewed PR26674, and it seems correct to me to handle this the same in getFunctionIndexForFile as in getModuleForFile. If we aren't including the object file in the link we don't care about any of its summary info.

[eugenis]

Thanks, committed as r262676

tools/gold/gold-plugin.cpp

 #include <vector>
 
 #ifndef LDPO_PIE
 // FIXME: remove this declaration when we stop maintaining Ubuntu Quantal and
 // Precise and Debian Wheezy (binutils 2.23 is required)
 # define LDPO_PIE 3
 #endif
 
+#define LDPT_GET_SYMBOLS_V3 28
+
 using namespace llvm;
 
 static ld_plugin_status discard_message(int level, const char *format, ...) {
   // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
   // callback in the transfer vector. This should never be called.
   abort();
 }
 
ld_plugin_status onload(ld_plugin_tv *tv) {
   // contain pointers to functions that we need to call to register our own
   // hooks. The others are addresses of functions we can use to call into gold
   // for services.
 
   bool registeredClaimFile = false;
   bool RegisteredAllSymbolsRead = false;
 
   for (; tv->tv_tag != LDPT_NULL; ++tv) {
-    switch (tv->tv_tag) {
+    // Cast tv_tag to int to allow values not in "enum ld_plugin_tag", like, for
+    // example, LDPT_GET_SYMBOLS_V3 when building against an older plugin-api.h
+    // header.
+    switch (static_cast<int>(tv->tv_tag)) {
       case LDPT_OUTPUT_NAME:
         output_name = tv->tv_u.tv_string;
         break;
       case LDPT_LINKER_OUTPUT:
         switch (tv->tv_u.tv_val) {
           case LDPO_REL:  // .o
           case LDPO_DYN:  // .so
           case LDPO_PIE:  // position independent executable
switch (static_cast<int>(tv->tv_tag)) {
         break;
       case LDPT_RELEASE_INPUT_FILE:
         release_input_file = tv->tv_u.tv_release_input_file;
         break;
       case LDPT_ADD_SYMBOLS:
         add_symbols = tv->tv_u.tv_add_symbols;
         break;
       case LDPT_GET_SYMBOLS_V2:
+        // Do not override get_symbols_v3 with get_symbols_v2.
+        if (!get_symbols) get_symbols = tv->tv_u.tv_get_symbols;
+        break;
+      case LDPT_GET_SYMBOLS_V3:
         get_symbols = tv->tv_u.tv_get_symbols;
         break;
       case LDPT_ADD_INPUT_FILE:
         add_input_file = tv->tv_u.tv_add_input_file;
         break;
       case LDPT_SET_EXTRA_LIBRARY_PATH:
         set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
         break;
static void freeSymName(ld_plugin_symbol &Sym) {
   free(Sym.name);
   free(Sym.comdat_key);
   Sym.name = nullptr;
   Sym.comdat_key = nullptr;
 }
 
 static std::unique_ptr<FunctionInfoIndex>
 getFunctionIndexForFile(claimed_file &F, ld_plugin_input_file &Info) {
+  ld_plugin_status status = get_symbols(F.handle, F.syms.size(), &F.syms[0]);
+  if (status == LDPS_NO_SYMS)
+    return nullptr;
 
-  if (get_symbols(F.handle, F.syms.size(), &F.syms[0]) != LDPS_OK)
+  if (status != LDPS_OK)
     message(LDPL_FATAL, "Failed to get symbol information");
 
   const void *View;
   if (get_view(F.handle, &View) != LDPS_OK)
     message(LDPL_FATAL, "Failed to get a view of file");
 
   MemoryBufferRef BufferRef(StringRef((const char *)View, Info.filesize),
                             Info.name);

 }
 
 static std::unique_ptr<Module>
 getModuleForFile(LLVMContext &Context, claimed_file &F,
                  ld_plugin_input_file &Info, raw_fd_ostream *ApiFile,
                  StringSet<> &Internalize, StringSet<> &Maybe,
                  std::vector<GlobalValue *> &Keep) {
 
-  if (get_symbols(F.handle, F.syms.size(), F.syms.data()) != LDPS_OK)
+  ld_plugin_status status = get_symbols(F.handle, F.syms.size(), F.syms.data());
+  if (status == LDPS_NO_SYMS)
+    return nullptr;
+
+  if (status != LDPS_OK)
     message(LDPL_FATAL, "Failed to get symbol information");
 
   const void *View;
   if (get_view(F.handle, &View) != LDPS_OK)
     message(LDPL_FATAL, "Failed to get a view of file");
 
   MemoryBufferRef BufferRef(StringRef((const char *)View, Info.filesize),
                             Info.name);
static ld_plugin_status allSymbolsReadHook(raw_fd_ostream *ApiFile) {
 
   StringSet<> Internalize;
   StringSet<> Maybe;
   for (claimed_file &F : Modules) {
     PluginInputFile InputFile(F.handle);
     std::vector<GlobalValue *> Keep;
     std::unique_ptr<Module> M = getModuleForFile(
         Context, F, InputFile.file(), ApiFile, Internalize, Maybe, Keep);
+    if (!M.get()) continue;
     if (!options::triple.empty())
       M->setTargetTriple(options::triple.c_str());
     else if (M->getTargetTriple().empty())
       M->setTargetTriple(DefaultTriple);
 
     if (L.move(std::move(M), Keep, [](GlobalValue &, IRMover::ValueAdder) {}))
       message(LDPL_FATAL, "Failed to link module");
   }