Export functions even if outputting wasm object file

src/wcc/emit_wasm.c

@@ -403,6 +403,32 @@ static void emit_global_section(EmitWasm *ew) {
   }
 }
 
+static void emit_export_section(EmitWasm *ew) {
+  Vector *exports = ew->exports;
+  if (exports == NULL || exports->len <= 0)
+    return;
+
+  DataStorage exports_section;
+  data_init(&exports_section);
+  data_open_chunk(&exports_section);
+  data_open_chunk(&exports_section);
+  for (int i = 0; i < exports->len; ++i) {
+    const Name *name = exports->data[i];
+
+    FuncInfo *info = table_get(&func_info_table, name);
+    assert(info != NULL);
+
+    data_string(&exports_section, name->chars, name->bytes);  // export name
+    data_uleb128(&exports_section, -1, IMPORT_FUNC);  // export kind
+    data_uleb128(&exports_section, -1, info->index);  // export func index
+  }
+  data_close_chunk(&exports_section, exports->len);  // num exports
+  data_close_chunk(&exports_section, -1);
+
+  fputc(SEC_EXPORT, ew->ofp);
+  fwrite(exports_section.buf, exports_section.len, 1, ew->ofp);
+}
+
 static void emit_elems_section(EmitWasm *ew) {
   int count = indirect_function_table.count;
   if (count == 0)
@@ -774,12 +800,13 @@ static void emit_reloc_data_section(EmitWasm *ew, Vector *reloc_data) {
   emit_reloc_section(ew, ew->data_section_index, reloc_data, kRelocData);
 }
 
-void emit_wasm(FILE *ofp, const char *import_module_name) {
+void emit_wasm(FILE *ofp, const char *import_module_name, Vector *exports) {
   write_wasm_header(ofp);
 
   EmitWasm ew_body = {
     .ofp = ofp,
     .import_module_name = import_module_name,
+    .exports = exports,
   };
   EmitWasm *ew = &ew_body;
 
@@ -798,6 +825,9 @@ void emit_wasm(FILE *ofp, const char *import_module_name) {
   // Globals.
   emit_global_section(ew);
 
+  // Exports.
+  emit_export_section(ew);
+
   // Elements.
   emit_elems_section(ew);
 

src/wcc/wcc.c

@@ -121,7 +121,7 @@ static void compilec(FILE *ppin, const char *filename, Vector *toplevel) {
 }
 
 int compile_csource(const char *src, enum OutType out_type, const char *ofn, Vector *ld_cmd,
-                    const char *import_module_name) {
+                    const char *import_module_name, Vector *exports) {
   FILE *ppout;
   if (out_type == OutPreprocess)
     ppout = ofn != NULL ? fopen(ofn, "w") : stdout;
@@ -181,6 +181,19 @@ int compile_csource(const char *src, enum OutType out_type, const char *ofn, Vec
   if (cc_flags.warn_as_error && compile_warning_count != 0)
     return 2;
 
+  if (exports != NULL) {
+    int undef = 0;
+    for (int i = 0; i < exports->len; ++i) {
+      const Name *name = exports->data[i];
+      if (!table_try_get(&func_info_table, name, NULL)) {
+        fprintf(stderr, "Export: `%.*s' not defined\n", NAMES(name));
+        ++undef;
+      }
+    }
+    if (undef > 0)
+      return 3;
+  }
+
   FILE *ofp;
   const char *outfn = NULL;
   if (out_type >= OutExecutable) {
@@ -205,7 +218,7 @@ int compile_csource(const char *src, enum OutType out_type, const char *ofn, Vec
   if (ofp == NULL) {
     error("Cannot open output file");
   } else {
-    emit_wasm(ofp, import_module_name);
+    emit_wasm(ofp, import_module_name, exports);
     assert(compile_error_count == 0);
     fclose(ofp);
   }
@@ -547,7 +560,8 @@ static int do_compile(Options *opts) {
       return 1;  // exit
     case Clanguage:
       {
-        int res = compile_csource(src, opts->out_type, outfn, obj_files, opts->import_module_name);
+        Vector *exports = opts->out_type < OutExecutable ? opts->exports : NULL;
+        int res = compile_csource(src, opts->out_type, outfn, obj_files, opts->import_module_name, exports);
         if (res != 0)
           return 1;  // exit
       }
@@ -564,6 +578,16 @@ static int do_compile(Options *opts) {
 
   if (opts->out_type < OutExecutable)
     return 0;
+
+  if (opts->entry_point == NULL) {
+    opts->entry_point = "_start";
+  }
+  if (opts->entry_point != NULL && *opts->entry_point != '\0') {
+    vec_push(opts->exports, alloc_name(opts->entry_point, NULL, false));
+  } else if (opts->exports->len == 0) {
+    error("no exports (require -e<xxx>)\n");
+  }
+
   return do_link(obj_files, opts);
 }
 
@@ -605,15 +629,6 @@ int main(int argc, char *argv[]) {
     add_inc_path(INC_AFTER, JOIN_PATHS(root, "include"));
   }
 
-  if (opts.out_type >= OutExecutable && opts.entry_point == NULL) {
-    opts.entry_point = "_start";
-  }
-  if (opts.entry_point != NULL && *opts.entry_point != '\0')
-    vec_push(opts.exports, alloc_name(opts.entry_point, NULL, false));
-  if (opts.exports->len == 0 && opts.out_type >= OutExecutable) {
-    error("no exports (require -e<xxx>)\n");
-  }
-
   VERBOSES("### Exports\n");
   for (int i = 0; i < opts.exports->len; ++i) {
     const Name *name = opts.exports->data[i];

src/wcc/wcc.h

@@ -106,6 +106,7 @@ void install_builtins(void);
 typedef struct {
   FILE *ofp;
   const char *import_module_name;
+  Vector *exports;
   Vector *data_segments;
   uint32_t section_index;
   uint32_t function_count;
@@ -114,7 +115,7 @@ typedef struct {
   uint32_t import_global_count;
 } EmitWasm;
 
-void emit_wasm(FILE *ofp, const char *import_module_name);
+void emit_wasm(FILE *ofp, const char *import_module_name, Vector *exports);
 
 void emit_type_section(EmitWasm *ew);
 void emit_tag_section(EmitWasm *ew);