Remove some magic handling of native shared libraries (#20886)

We had this rather strange (I imagine completely unused) feature where
is emscripten is passed a concrete path to a shared library file (e.g.
/path/to/libfoo.so) and it could determine that the shared library was
not indented for emscripten then it would instead search the library
for other things called `libfoo` that might work.

This seems too magical at best and harmful/confusing a worst.

The presence of this feature is blocking the way for some internal
optimizations and refactorings (e.g. #20884)

Author: sbc100

ChangeLog.md

@@ -23,6 +23,17 @@ See docs/process.md for more on how version tagging works.
 - Support for explicitly targeting the legacy Interet Explorer or EdgeHTML
   (edge version prior to the chromium-based edge) browsers via
   `-sMIN_EDGE_VERSION/-sMIN_IE_VERSION` was removed. (#20881)
+- Emscripten is now more strict about handling unsupported shared library
+  inputs.  For example, under the old behaviour if a system shared library
+  such as `/usr/lib/libz.so` was passed to emscripten it would silently re-write
+  this to `-lz`, which would then search this a libz in its own sysroot.  Now
+  this file is passed though the linker like any other input file and you will
+  see an `unknown file type` error from the linker (just like you would with the
+  native clang or gcc toolchains). (#20886)
+- Support for explicitly targeting the legacy EdgeHTML browser (edge version
+  prior to the chromium-based edge) via `-sMIN_EDGE_VERSION` was removed.
+  Using `-sLEGACY_VM_SUPPORT` should still work if anyone still wanted to target
+  this or any other legacy browser.
 - Breaking change: Using the `*glGetProcAddress()` family of functions now
   requires passing a linker flag -sGL_ENABLE_GET_PROC_ADDRESS. This prevents
   ports of native GL renderers from later accidentally attempting to activate

emcc.py

@@ -761,16 +761,7 @@ def phase_setup(options, state, newargs):
         else:
           message = arg + ': Unknown format, not a static library!'
         exit_with_error(message)
-      if file_suffix in DYNAMICLIB_ENDINGS and not building.is_bitcode(arg) and not building.is_wasm(arg):
-        # For shared libraries that are neither bitcode nor wasm, assuming its local native
-        # library and attempt to find a library by the same name in our own library path.
-        # TODO(sbc): Do we really need this feature?  See test_other.py:test_local_link
-        libname = removeprefix(get_library_basename(arg), 'lib')
-        flag = '-l' + libname
-        diagnostics.warning('map-unrecognized-libraries', f'unrecognized file type: `{arg}`.  Mapping to `{flag}` and hoping for the best')
-        state.add_link_flag(i, flag)
-      else:
-        input_files.append((i, arg))
+      input_files.append((i, arg))
     elif arg.startswith('-L'):
       state.add_link_flag(i, arg)
       newargs[i] = ''

test/test_other.py

@@ -1642,33 +1642,6 @@ def test_abspaths(self):
       WARNING = 'encountered. If this is to a local system header/library, it may cause problems (local system files make sense for compiling natively on your system, but not necessarily to JavaScript)'
       self.assertContainedIf(WARNING, proc.stderr, expected)
 
-  def test_local_link(self):
-    # Linking a local library directly, like /usr/lib/libsomething.so, cannot work of course since it
-    # doesn't contain bitcode. However, when we see that we should look for a bitcode file for that
-    # library in the -L paths and system/lib
-    create_file('main.c', '''
-      extern void printey();
-      int main() {
-        printey();
-        return 0;
-      }
-    ''')
-
-    ensure_dir('subdir')
-    create_file('subdir/libfile.so.1.2.3', 'this is not llvm bitcode!')
-
-    create_file('libfile.c', '''
-      #include <stdio.h>
-      void printey() {
-        printf("hello from lib\\n");
-      }
-    ''')
-
-    self.run_process([EMCC, 'libfile.c', '-shared', '-o', 'libfile.so'], stderr=PIPE)
-    err = self.run_process([EMCC, 'main.c', Path('subdir/libfile.so.1.2.3'), '-L.'], stderr=PIPE).stderr
-    self.assertContained('Mapping to `-lfile` and hoping for the best [-Wmap-unrecognized-libraries]', err)
-    self.assertContained('hello from lib', self.run_js('a.out.js'))
-
   def test_identical_basenames(self):
     # Issue 287: files in different dirs but with the same basename get confused as the same,
     # causing multiply defined symbol errors