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

@@ -106,8 +106,8 @@ def update_settings_glue(wasm_file, metadata, base_metadata):
     # we don't need any JS library contents in side modules
     settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE = []
   else:
-    syms = settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE + metadata.imports
-    syms = set(syms).difference(metadata.all_exports)
+    syms = set(settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE).difference(metadata.all_exports)
+    syms.update(metadata.imports)
     settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE = sorted(syms)
     if settings.MAIN_MODULE:
       settings.WEAK_IMPORTS += webassembly.get_weak_imports(wasm_file)
@@ -1020,6 +1020,10 @@ def create_receiving(function_exports, other_exports, library_symbols, aliases):
     # folks try to call/use a reference that was taken before the
     # wasm module is available.
     for sym in mangled:
+      # Don't generate early access traps for symbols that are also JS
+      # library functions
+      if sym in library_symbols:
+        continue
       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:
         continue