Fix: When symbol is both imported and exported, don't drop import

This fixes wrapping syscalls with -sMAIN_MODULE and -sEXPORT_ALL. Resolves issue 26355.

Author: hoodmane

src/jsifier.mjs

@@ -559,7 +559,7 @@ function(${args}) {
 
       // if the function was implemented in compiled code, there is no need to
       // include the js version
-      if (WASM_EXPORTS.has(symbol)) {
+      if (WASM_EXPORTS.has(symbol) && !DEFAULT_LIBRARY_FUNCS_TO_INCLUDE.includes(symbol)) {
         return;
       }
 

test/test_other.py

@@ -1607,6 +1607,31 @@ def test_export_all(self):
     # Without the `-sEXPORT_ALL` these symbols will not be visible from JS
     self.do_runf('main.c', '_libf1 is not defined', assert_returncode=NON_ZERO, cflags=['-Oz', '-sMAIN_MODULE', '--pre-js', 'pre.js'])
 
+  def test_export_all_syscall_override(self):
+    create_file('main.c', r'''
+      #include "stdio.h"
+      #include <fcntl.h>
+
+      int syscall_openat_orig(int dirfd, intptr_t path, int flags, void* varags)
+          __attribute__((__import_module__("env"),
+                        __import_name__("__syscall_openat"), __warn_unused_result__));
+
+      int __syscall_openat(int dirfd, intptr_t path, int flags, void* varargs) {
+          printf("__syscall_openat!\n");
+          return syscall_openat_orig(dirfd, path, flags, varargs);
+      }
+
+      int main() {
+          int fd = open("a.c", O_RDONLY);
+          printf("fd: %d\n", fd);
+      }
+    ''')
+
+    self.do_runf('main.c', '__syscall_openat!', cflags=['-sEXPORT_ALL', '-sNODERAWFS'])
+    self.do_runf('main.c', '__syscall_openat!', cflags=['-sMAIN_MODULE', '-sNODERAWFS'])
+    self.do_runf('main.c', '__syscall_openat!', cflags=['-O2', '-sEXPORT_ALL', '-sMAIN_MODULE', '-sNODERAWFS'])
+    self.do_runf('main.c', '__syscall_openat!', cflags=['-sEXPORT_ALL', '-sMAIN_MODULE', '-sNODERAWFS'])
+
   def test_export_keepalive(self):
     create_file('main.c', r'''
       #include <emscripten.h>

tools/emscripten.py

@@ -969,7 +969,7 @@ def should_export(sym):
   return settings.EXPORT_ALL or (settings.EXPORT_KEEPALIVE and sym in settings.EXPORTED_FUNCTIONS)
 
 
-def create_receiving(function_exports, other_exports, library_symbols, aliases):
+def create_receiving(function_exports, other_exports, library_symbols, aliases, wasm_imports):
   generate_dyncall_assignment = 'dynCalls' in library_symbols
   receiving = ['\n// Imports from the Wasm binary.']
 
@@ -1019,6 +1019,7 @@ def create_receiving(function_exports, other_exports, library_symbols, aliases):
     # In debug builds we generate trapping functions in case
     # folks try to call/use a reference that was taken before the
     # wasm module is available.
+    wasm_imports_mangled = {asmjs_mangle(s) for s in wasm_imports}
     for sym in mangled:
       module_export = (settings.MODULARIZE or not settings.MINIMAL_RUNTIME) and should_export(sym) and settings.MODULARIZE != 'instance'
       if not js_manipulation.isidentifier(sym) and not module_export:
@@ -1029,7 +1030,11 @@ def create_receiving(function_exports, other_exports, library_symbols, aliases):
           assignment += f" = Module['{sym}']"
         else:
           assignment = f"Module['{sym}']"
-      receiving.append(f"{assignment} = makeInvalidEarlyAccess('{sym}');")
+      # Don't generate early access traps for symbols that are also wasm imports.
+      if sym in wasm_imports_mangled:
+        receiving.append(f"{assignment};")
+      else:
+        receiving.append(f"{assignment} = makeInvalidEarlyAccess('{sym}');")
   else:
     # Declare all exports in a single var statement
     sep = ',\n  '
@@ -1100,7 +1105,7 @@ def create_receiving(function_exports, other_exports, library_symbols, aliases):
 
 def create_module(metadata, function_exports, other_exports, library_symbols, aliases):
   module = []
-  module.append(create_receiving(function_exports, other_exports, library_symbols, aliases))
+  module.append(create_receiving(function_exports, other_exports, library_symbols, aliases, metadata.imports))
 
   sending = create_sending(metadata, library_symbols)
   if settings.WASM_ESM_INTEGRATION: