@@ -50,6 +50,13 @@ struct LLVMOpt : public Pass {
5050 for (auto & e : module ->exports ) {
5151 originalExports.insert (e->name );
5252 }
53+ // We will add additional exports, some of which we can forget about
54+ // imediately, but others we need to keep around until almost the very end
55+ // because we need to use them.
56+ // For example, we add an export for the start function if there is one, and
57+ // we find it in the output wasm and use it to find the start function. We
58+ // can then remove the export
59+ std::set<Name> usedExports;
5360
5461 // Add exports for more things that we need, either for the wasm2c runtime,
5562 // or to make it easy for us to find what we need afterwards. (We will
@@ -65,10 +72,18 @@ struct LLVMOpt : public Pass {
6572 }
6673 // Ensure a _start is exported, which wasm2c expects.
6774 if (!module ->getExportOrNull (" _start"
75+ Name name (" byn_llvm_runtime_start"
6876 module ->addFunction (builder.makeFunction (
69- " byn$llvm-start " makeNop ()));
77+ name , {Type::none, Type::none}, {}, builder.makeNop ()));
7078 module ->addExport (
71- builder.makeExport (" _start" " byn$llvm-start"
79+ builder.makeExport (" _start"
80+ }
81+ // Export the wasm start function, if there is one.
82+ Name wasmStartExport (" byn_llvm_wasm_start"
83+ if (module ->start .is ()) {
84+ module ->addExport (
85+ builder.makeExport (wasmStartExport, module ->start , ExternalKind::Function));
86+ usedExports.insert (wasmStartExport);
7287 }
7388
7489 // Write the module to a temp file.
@@ -103,14 +118,18 @@ struct LLVMOpt : public Pass {
103118 std::string cmd =
104119 " emcc " " -o " " -O1 -s EXPORTED_FUNCTIONS="
105120 bool first = true ;
106- for (auto e : originalExports) {
107- if (first) {
108- first = false ;
109- } else {
110- cmd += ' ,'
121+ auto addExports = [&](const std::set<Name>& names) {
122+ for (auto e : names) {
123+ if (first) {
124+ first = false ;
125+ } else {
126+ cmd += ' ,'
127+ }
128+ cmd += std::string (" _w2c_" str ;
111129 }
112- cmd += std::string (" _w2c_" str ;
113- }
130+ };
131+ addExports (originalExports);
132+ addExports (usedExports);
114133 ProgramResult c2wasm (cmd);
115134 if (c2wasm.failed ()) {
116135 c2wasm.dump (std::cout);
@@ -135,6 +154,11 @@ struct LLVMOpt : public Pass {
135154 return false ;
136155 }),
137156 module ->exports .end ());
157+ module ->updateMaps ();
158+ // Find the important things we exported so that we could find them later.
159+ if (auto * e = module ->getExportOrNull (wasmStartExport)) {
160+ module ->start = e->value ;
161+ }
138162 // Remove the table: the "native" table contains things the new sandboxing
139163 // layer in C added and needs. We want to look into the wasm in that
140164 // sandbox.
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