Add reference to extension object to class_map

Add IDL component:
{
  "extension": {
    "symbol": "s_foo_extension"
  }
}

extension.symbol is the C++ HPHP::Extension symbol for the
extension (if one exists and is exported).

hphp/runtime/base/class_info.cpp

@@ -21,6 +21,7 @@
 #include "hphp/runtime/base/hphp_system.h"
 #include "hphp/runtime/base/variable_serializer.h"
 #include "hphp/runtime/base/variable_unserializer.h"
+#include "hphp/runtime/ext/extension.h"
 #include "hphp/util/util.h"
 #include "hphp/util/lock.h"
 #include "hphp/util/logger.h"
@@ -745,6 +746,14 @@ void ClassInfoUnique::postInit() {
 void ClassInfo::Load() {
   if (s_loaded) return;
   const char **p = g_class_map;
+
+  while (*p) {
+    Extension *ext = (Extension*)*p++;
+    // TODO: Do something useful with this
+    // For now, it's here to anchor "empty" extensions
+  }
+  p++;
+
   while (*p) {
     Attribute attribute = (Attribute)(int64_t)*p;
     always_assert(!(attribute & IsRedeclared));

hphp/tools/bootstrap/gen-class-map.cpp

@@ -317,7 +317,8 @@ static void writeClass(std::ostream& out, const PhpClass& cls) {
 static void outputClassMap(const char *outputfn, const char *classmap_name,
                            const fbvector<PhpClass>& classes,
                            const fbvector<PhpFunc>& funcs,
-                           const fbvector<PhpConst>& consts) {
+                           const fbvector<PhpConst>& consts,
+                           const fbvector<PhpExtension>& exts) {
   std::ofstream out(outputfn);
 
   out << "// @" "generated by gen-class-map.cpp\n"
@@ -325,8 +326,17 @@ static void outputClassMap(const char *outputfn, const char *classmap_name,
       << "#include \"hphp/runtime/ext/ext.h\"\n"
       << "namespace HPHP {\n";
   declareConstants(out, consts, false);
-  out << "const char *" << classmap_name << "[] = {\n"
-      << "  (const char *)ClassInfo::IsSystem, NULL, "
+  out << "const char *" << classmap_name << "[] = {\n";
+
+  for (auto &e : exts) {
+    auto sym = e.symbol();
+    if (!sym.empty()) {
+      out << "  (const char*)&" << sym << ",\n";
+    }
+  }
+  out << "  NULL,\n"; // End of extensions
+
+  out << "  (const char *)ClassInfo::IsSystem, NULL, "
       << "\"\", \"\", NULL, NULL, NULL,\n";
   for (auto &f : funcs) {
     writeFunction(out, f);
@@ -377,10 +387,11 @@ int main(int argc, const char* argv[]) {
   fbvector<PhpFunc> funcs;
   fbvector<PhpClass> classes;
   fbvector<PhpConst> consts;
+  fbvector<PhpExtension> exts;
 
   for (int i = (system ? 4 : 3); i < argc; ++i) {
     try {
-      parseIDL(argv[i], funcs, classes, consts);
+      parseIDL(argv[i], funcs, classes, consts, exts);
     } catch (const std::exception& exc) {
       std::cerr << argv[i] << ": " << exc.what() << "\n";
       return 1;
@@ -389,7 +400,7 @@ int main(int argc, const char* argv[]) {
 
   const char* path = argv[2];
   const char* name = (system ? "g_class_map" : argv[1]);
-  outputClassMap(path, name, classes, funcs, consts);
+  outputClassMap(path, name, classes, funcs, consts, exts);
   if (system) {
     path = argv[3];
     outputConstants(path, consts);

hphp/tools/bootstrap/idl.cpp

@@ -699,7 +699,8 @@ PhpClass::PhpClass(const folly::dynamic &c) :
 void parseIDL(const char* idlFilePath,
               fbvector<PhpFunc>& funcVec,
               fbvector<PhpClass>& classVec,
-              fbvector<PhpConst>& constVec) {
+              fbvector<PhpConst>& constVec,
+              fbvector<PhpExtension>& extVec) {
   std::ostringstream jsonString;
   std::ifstream infile(idlFilePath);
   infile >> jsonString.rdbuf();
@@ -718,13 +719,19 @@ void parseIDL(const char* idlFilePath,
     PhpConst cns(c);
     constVec.push_back(cns);
   }
+  auto it = parsed.find("extension");
+  if (it != parsed.items().end()) {
+    PhpExtension ext(it->second);
+    extVec.push_back(ext);
+  }
 }
 
 void parseIDL(const char* idlFilePath,
               fbvector<PhpFunc>& funcVec,
               fbvector<PhpClass>& classVec) {
   fbvector<PhpConst> consts; // dummy
-  parseIDL(idlFilePath, funcVec, classVec, consts);
+  fbvector<PhpExtension> exts; // dummy
+  parseIDL(idlFilePath, funcVec, classVec, consts, exts);
 }
 
 /////////////////////////////////////////////////////////////////////////////

hphp/tools/bootstrap/idl.h

@@ -371,6 +371,27 @@ class PhpClass {
   fbstring m_desc;
 };
 
+class PhpExtension {
+ public:
+  explicit PhpExtension(const folly::dynamic& e)
+    : m_extension(e) { }
+
+  /* The C++ symbol name of the Extension struct.
+   * Only needed if s_(name)_extension is not correct.
+   * Set to blank if this ext doens't declare an Extension.
+   */
+  fbstring symbol() const {
+    auto it = m_extension.find("symbol");
+    if (it != m_extension.items().end()) {
+      return it->second.asString();
+    }
+    return "";
+  }
+
+ private:
+  folly::dynamic m_extension;
+};
+
 void parseIDL(const char* idlFilePath,
               fbvector<PhpFunc>& funcVec,
               fbvector<PhpClass>& classVec);
@@ -378,7 +399,8 @@ void parseIDL(const char* idlFilePath,
 void parseIDL(const char* idlFilePath,
               fbvector<PhpFunc>& funcVec,
               fbvector<PhpClass>& classVec,
-              fbvector<PhpConst>& constVec);
+              fbvector<PhpConst>& constVec,
+              fbvector<PhpExtension>& extVec);
 
 /////////////////////////////////////////////////////////////////////////////
 }} // namespace HPHP::IDL