Avoid converting use JS paths to absolute paths. NFC

System library paths are converted to absolute paths, both in link.py
and in modules.mjs, but use JS libraries are left in their original
form.

Added a test to confirm that a user library can have the same name
as as system library without issue.

Split out from emscripten-core#23787

Author: sbc100

src/modules.mjs

@@ -201,20 +201,15 @@ function calculateLibraries() {
     libraries.push('liblittle_endian_heap.js');
   }
 
+  // Resolve system libraries
+  libraries = libraries.map((filename) => path.join(systemLibdir, filename));
+
   // Add all user specified JS library files to the link.
   // These must be added last after all Emscripten-provided system libraries
   // above, so that users can override built-in JS library symbols in their
   // own code.
   libraries.push(...JS_LIBRARIES);
 
-  // Resolve all filenames to absolute paths
-  libraries = libraries.map((filename) => {
-    if (!path.isAbsolute(filename) && fs.existsSync(path.join(systemLibdir, filename))) {
-      filename = path.join(systemLibdir, filename);
-    }
-    return path.resolve(filename);
-  });
-
   // Deduplicate libraries to avoid processing any library file multiple times
   libraries = libraries.filter((item, pos) => libraries.indexOf(item) == pos);
 

test/test_other.py

@@ -5001,6 +5001,23 @@ def test_jslib_new_objects_non_empty(self):
     err = self.expect_fail([EMCC, test_file('hello_world.c'), '--js-library=lib.js', '-sEXPORTED_FUNCTIONS=obj,_main'])
     self.assertContained('cannot stringify Map with data', err)
 
+  def test_jslib_system_lib_name(self):
+    create_file('libcore.js', r'''
+addToLibrary({
+ jslibfunc: (x) => 2 * x
+});
+''')
+    create_file('src.c', r'''
+#include <emscripten.h>
+#include <stdio.h>
+int jslibfunc(int x);
+int main() {
+  printf("jslibfunc: %d\n", jslibfunc(6));
+  return 0;
+}
+''')
+    self.do_runf('src.c', 'jslibfunc: 12', emcc_args=['--js-library', 'libcore.js'])
+
   def test_EMCC_BUILD_DIR(self):
     # EMCC_BUILD_DIR was necessary in the past since we used to force the cwd to be src/ for
     # technical reasons.

tools/link.py

@@ -217,8 +217,6 @@ def get_js_sym_info():
   assert jslibs
   input_files.extend(read_file(jslib) for jslib in sorted(jslibs))
   for jslib in settings.JS_LIBRARIES:
-    if not os.path.isabs(jslib):
-      jslib = utils.path_from_root('src/lib', jslib)
     input_files.append(read_file(jslib))
   content = '\n'.join(input_files)
   content_hash = hashlib.sha1(content.encode('utf-8')).hexdigest()
@@ -1246,7 +1244,7 @@ def phase_linker_setup(options, linker_args):  # noqa: C901, PLR0912, PLR0915
   if settings.WASMFS:
     settings.FILESYSTEM = 1
     settings.SYSCALLS_REQUIRE_FILESYSTEM = 0
-    settings.JS_LIBRARIES.append('libwasmfs.js')
+    add_system_js_lib('libwasmfs.js')
     if settings.ASSERTIONS:
       # used in assertion checks for unflushed content
       settings.REQUIRED_EXPORTS += ['wasmfs_flush']
@@ -1362,14 +1360,14 @@ def phase_linker_setup(options, linker_args):  # noqa: C901, PLR0912, PLR0915
 
   if settings.PTHREADS:
     setup_pthreads()
-    settings.JS_LIBRARIES.append('libpthread.js')
+    add_system_js_lib('libpthread.js')
     if settings.PROXY_TO_PTHREAD:
       settings.PTHREAD_POOL_SIZE_STRICT = 0
       settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$runtimeKeepalivePush']
   else:
     if settings.PROXY_TO_PTHREAD:
       exit_with_error('-sPROXY_TO_PTHREAD requires -pthread to work!')
-    settings.JS_LIBRARIES.append('libpthread_stub.js')
+    add_system_js_lib('libpthread_stub.js')
 
   if settings.MEMORY64:
     # Any "pointers" passed to JS will now be i64's, in both modes.
@@ -1383,7 +1381,7 @@ def phase_linker_setup(options, linker_args):  # noqa: C901, PLR0912, PLR0915
     # set location of Wasm Worker bootstrap JS file
     if settings.WASM_WORKERS == 1:
       settings.WASM_WORKER_FILE = unsuffixed(os.path.basename(target)) + '.ww.js'
-    settings.JS_LIBRARIES.append('libwasm_worker.js')
+    add_system_js_lib('libwasm_worker.js')
 
   # Set min browser versions based on certain settings such as WASM_BIGINT,
   # PTHREADS, AUDIO_WORKLET
@@ -1401,7 +1399,7 @@ def phase_linker_setup(options, linker_args):  # noqa: C901, PLR0912, PLR0915
   if settings.AUDIO_WORKLET:
     if settings.AUDIO_WORKLET == 1:
       settings.AUDIO_WORKLET_FILE = unsuffixed(os.path.basename(target)) + '.aw.js'
-    settings.JS_LIBRARIES.append('libwebaudio.js')
+    add_system_js_lib('libwebaudio.js')
     if not settings.MINIMAL_RUNTIME:
       # If we are in the audio worklet environment, we can only access the Module object
       # and not the global scope of the main JS script. Therefore we need to export
@@ -2767,14 +2765,20 @@ def map_to_js_libs(library_name):
   return None
 
 
+def add_system_js_lib(lib):
+  lib = utils.path_from_root('src/lib', lib)
+  assert os.path.exists(lib)
+  settings.JS_LIBRARIES.append(lib)
+
+
 def process_libraries(options, flags):
   new_flags = []
   system_libs_map = system_libs.Library.get_usable_variations()
 
   # Process `-l` and `--js-library` flags
   for flag in flags:
     if flag.startswith('--js-library='):
-      js_lib = os.path.abspath(flag.split('=', 1)[1])
+      js_lib = flag.split('=', 1)[1]
       settings.JS_LIBRARIES.append(js_lib)
       continue
     if not flag.startswith('-l'):
@@ -2784,9 +2788,8 @@ def process_libraries(options, flags):
 
     logger.debug('looking for library "%s"', lib)
 
-    js_libs = map_to_js_libs(lib)
-    if js_libs is not None:
-      settings.JS_LIBRARIES += js_libs
+    for lib in map_to_js_libs(lib):
+      add_system_js_lib(lib)
 
     # We don't need to resolve system libraries to absolute paths here, we can just
     # let wasm-ld handle that.  However, we do want to map to the correct variant.