Add option: allow-undefined

Author: tyfkda

README.md

@@ -114,6 +114,8 @@ Command line options:
   * `-nodefaultlibs`:  Ignore libc
   * `-nostdlib`:  Ignore libc and crt0
   * `--verbose`:  Output debug information
+  * `-Wl,...`:       Linker option
+    * `--allow-undefined`:  Handles unresolved function symbols as imported on runtime
 
 #### Run
 

src/_debug/wcc-ld.c

@@ -28,16 +28,22 @@ int main(int argc, char *argv[]) {
     OPT_VERBOSE = 256,
     OPT_ENTRY_POINT,
     OPT_STACK_SIZE,
+    OPT_ALLOW_UNDEFINED,
   };
   static const struct option kOptions[] = {
     {"o", required_argument},  // Specify output filename
     {"-verbose", no_argument, OPT_VERBOSE},
     {"-entry-point", required_argument, OPT_ENTRY_POINT},
     {"-stack-size", required_argument, OPT_STACK_SIZE},
+    {"-allow-undefined", no_argument, OPT_ALLOW_UNDEFINED},
 
     {NULL},
   };
 
+  WasmLinker linker_body;
+  WasmLinker *linker = &linker_body;
+  linker_init(linker);
+
   int opt;
   while ((opt = optparse(argc, argv, kOptions)) != -1) {
     switch (opt) {
@@ -69,17 +75,16 @@ int main(int argc, char *argv[]) {
         stack_size = size;
       }
       break;
+    case OPT_ALLOW_UNDEFINED:
+      linker->options.allow_undefined = true;
+      break;
     case '?':
       fprintf(stderr, "Warning: unknown option: %s\n", argv[optind - 1]);
       break;
     }
   }
   int iarg = optind;
 
-  WasmLinker linker_body;
-  WasmLinker *linker = &linker_body;
-  linker_init(linker);
-
   bool result = true;
   for (int i = iarg; i < argc; ++i) {
     const char *src = argv[i];

src/wcc/wasm_linker.c

@@ -767,7 +767,8 @@ static bool resolve_symbols(WasmLinker *linker) {
     switch (sym->kind) {
     default: assert(false); // Fallthrough to suppress warning.
     case SIK_SYMTAB_FUNCTION:
-      if (sym->module_name != NULL && equal_name(sym->module_name, wasi_module_name)) {
+      if ((sym->module_name != NULL && equal_name(sym->module_name, wasi_module_name)) ||
+          linker->options.allow_undefined) {
         sym->combined_index = unresolved_func_count++;
         break;
       }
@@ -1218,6 +1219,7 @@ static void out_import_section(WasmLinker *linker) {
   const Name *name;
   SymbolInfo *sym;
   for (int it = 0; (it = table_iterate(&linker->unresolved, it, &name, (void**)&sym)) != -1; ) {
+    assert(sym != NULL);
     if (sym->kind != SIK_SYMTAB_FUNCTION)
       continue;
     const Name *modname = sym->module_name;

src/wcc/wasm_linker.h

@@ -11,13 +11,19 @@ typedef struct Vector Vector;
 
 #define WASI_MODULE_NAME  "wasi_snapshot_preview1"
 
+typedef struct {
+  bool allow_undefined;
+} WasmLinkerOptions;
+
 typedef struct {
   Vector *files;  // <File*>
   Table defined, unresolved;  // <SymbolInfo*>
   Vector *indirect_functions;  // public/static indirect functions, <SymbolInfo*>
   uint32_t unresolved_func_count;
   uint32_t address_bottom;
 
+  WasmLinkerOptions options;
+
   const Name *sp_name;
   const Name *curbrk_name;
   const Name *indirect_function_table_name;

src/wcc/wcc.c

@@ -45,6 +45,8 @@ typedef struct {
   enum SourceType src_type;
   uint32_t stack_size;
   bool nodefaultlibs, nostdlib, nostdinc;
+
+  WasmLinkerOptions linker_opts;
 } Options;
 
 static Vector remove_on_exit;
@@ -232,6 +234,38 @@ int compile_csource(const char *src, const char *ofn, Vector *obj_files, Options
   return 0;
 }
 
+static void parse_linker_options(const char *arg, WasmLinkerOptions *lopts) {
+  const char *arg_bak = arg;
+  if (*arg != '-')
+    return;
+  ++arg;
+
+  enum {
+    OPT_ALLOW_UNDEFINED,
+  };
+  static const struct option kOptions[] = {
+    {"-allow-undefined", no_argument, OPT_ALLOW_UNDEFINED},
+
+    {NULL},
+  };
+
+  for (int i = 0; ; ++i) {
+    if (kOptions[i].name == NULL)
+      break;
+    if (strcmp(arg, kOptions[i].name) == 0) {
+      switch (kOptions[i].val) {
+      default: assert(false); break;
+      case OPT_ALLOW_UNDEFINED:
+        lopts->allow_undefined = true;
+        break;
+      }
+      return;
+    }
+  }
+  fprintf(stderr, "Warning: unknown option: %s\n", arg_bak);
+}
+
+
 static void parse_options(int argc, char *argv[], Options *opts) {
   enum {
     OPT_HELP = 128,
@@ -470,6 +504,11 @@ static void parse_options(int argc, char *argv[], Options *opts) {
             *p = true;
           break;
         }
+
+        const char *arg = argv[optind - 1];
+        if (strncmp(arg, "-Wl,", 4) == 0) {
+          parse_linker_options(arg + 4, &opts->linker_opts);
+        }
       }
       // Fallthrough
     case OPT_WNO:
@@ -534,6 +573,7 @@ static int do_link(Vector *obj_files, Options *opts) {
   WasmLinker linker_body;
   WasmLinker *linker = &linker_body;
   linker_init(linker);
+  linker->options = opts->linker_opts;
 
   for (int i = 0; i < obj_files->len; ++i) {
     const char *objfn = obj_files->data[i];