Deprecate RUNTIME_LINKED_LIBS setting. NFC

Its better to simply list dynamic library dependencies directly on the
command line.

Handle the deprecated option by simply added the list of libraries to
the command line.  This means we no longer need to modify the dylink
section after linking since the linker will inject all the needed
dynamic libraries that it sees on the command line.

Author: sbc100

ChangeLog.md

@@ -20,6 +20,9 @@ See docs/process.md for more on how version tagging works.
 
 Current Trunk
 -------------
+- The `RUNTIME_LINKED_LIBS` setting is now deprecated.  It's better to simply
+  list dynamic library dependencies directly on the command line.
+
 2.0.18: 04/23/2021
 ------------------
 - The `makeBigInt` function was removed from the emscripten runtime since it

emcc.py

@@ -1061,6 +1061,45 @@ def uniquename(name):
     explicit_settings_changes, newargs = parse_s_args(newargs)
     settings_changes += explicit_settings_changes
 
+    settings_map = {}
+    for s in settings_changes:
+      key, value = s.split('=', 1)
+      settings_map[key] = value
+
+    # Libraries are searched before settings_changes are applied, so apply the
+    # value for STRICT from command line already now.
+
+    strict_cmdline = settings_map.get('STRICT')
+    if strict_cmdline:
+      settings.STRICT = int(strict_cmdline)
+
+    # Apply optimization level settings
+
+    if settings.OPT_LEVEL >= 1:
+      settings.ASSERTIONS = 0
+    if settings.SHRINK_LEVEL >= 2:
+      settings.EVAL_CTORS = 1
+
+    # For users that opt out of WARN_ON_UNDEFINED_SYMBOLS we assume they also
+    # want to opt out of ERROR_ON_UNDEFINED_SYMBOLS.
+    if settings_map.get('WARN_ON_UNDEFINED_SYMBOLS') == '0':
+      settings.ERROR_ON_UNDEFINED_SYMBOLS = 0
+
+    if settings.MINIMAL_RUNTIME or settings_map.get('MINIMAL_RUNTIME') in ('1', '2'):
+      # Remove the default exported functions 'malloc', 'free', etc. those should only be linked in if used
+      settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE = []
+
+    # Apply -s settings in newargs here (after optimization levels, so they can override them)
+    apply_settings(settings_map)
+
+    if settings.EXTRA_EXPORTED_RUNTIME_METHODS:
+      diagnostics.warning('deprecated', 'EXTRA_EXPORTED_RUNTIME_METHODS is deprecated, please use EXPORTED_RUNTIME_METHODS instead')
+      settings.EXPORTED_RUNTIME_METHODS += settings.EXTRA_EXPORTED_RUNTIME_METHODS
+
+    if settings.RUNTIME_LINKED_LIBS:
+      diagnostics.warning('deprecated', 'RUNTIME_LINKED_LIBS is deprecated; you can simply list the libraries directly on the commandline now')
+      newargs += settings.RUNTIME_LINKED_LIBS
+
     # Find input files
 
     # These three arrays are used to store arguments of different types for
@@ -1165,37 +1204,6 @@ def add_link_flag(i, f):
 
     newargs = [a for a in newargs if a]
 
-    settings_map = {}
-    for s in settings_changes:
-      key, value = s.split('=', 1)
-      settings_map[key] = value
-
-    # Libraries are searched before settings_changes are applied, so apply the
-    # value for STRICT from command line already now.
-
-    strict_cmdline = settings_map.get('STRICT')
-    if strict_cmdline:
-      settings.STRICT = int(strict_cmdline)
-
-    # Apply optimization level settings
-
-    if settings.OPT_LEVEL >= 1:
-      settings.ASSERTIONS = 0
-    if settings.SHRINK_LEVEL >= 2:
-      settings.EVAL_CTORS = 1
-
-    # For users that opt out of WARN_ON_UNDEFINED_SYMBOLS we assume they also
-    # want to opt out of ERROR_ON_UNDEFINED_SYMBOLS.
-    if settings_map.get('WARN_ON_UNDEFINED_SYMBOLS') == '0':
-      settings.ERROR_ON_UNDEFINED_SYMBOLS = 0
-
-    if settings.MINIMAL_RUNTIME or settings_map.get('MINIMAL_RUNTIME') in ('1', '2'):
-      # Remove the default exported functions 'malloc', 'free', etc. those should only be linked in if used
-      settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE = []
-
-    # Apply -s settings in newargs here (after optimization levels, so they can override them)
-    apply_settings(settings_map)
-
     specified_target = options.output_file
 
     if os.environ.get('EMMAKEN_JUST_CONFIGURE') or 'conftest.c' in args:
@@ -1227,10 +1235,6 @@ def add_link_flag(i, f):
 
     settings.TARGET_BASENAME = target_basename = unsuffixed_basename(target)
 
-    if settings.EXTRA_EXPORTED_RUNTIME_METHODS:
-      diagnostics.warning('deprecated', 'EXTRA_EXPORTED_RUNTIME_METHODS is deprecated, please use EXPORTED_RUNTIME_METHODS instead')
-      settings.EXPORTED_RUNTIME_METHODS += settings.EXTRA_EXPORTED_RUNTIME_METHODS
-
     final_suffix = get_file_suffix(target)
 
     if has_dash_c or has_dash_S or has_dash_E or '-M' in newargs or '-MM' in newargs:
@@ -2925,10 +2929,6 @@ def do_binaryen(target, options, wasm_target):
 
   # after generating the wasm, do some final operations
 
-  # Add extra dylibs if needed.
-  if settings.RUNTIME_LINKED_LIBS:
-    webassembly.update_dylink_section(wasm_target, settings.RUNTIME_LINKED_LIBS)
-
   if settings.EMIT_EMSCRIPTEN_METADATA:
     diagnostics.warning('deprecated', 'We hope to remove support for EMIT_EMSCRIPTEN_METADATA. See https://github.com/emscripten-core/emscripten/issues/12231')
     webassembly.add_emscripten_metadata(wasm_target)

src/settings.js

@@ -973,10 +973,7 @@ var MAIN_MODULE = 0;
 // [compile+link]
 var SIDE_MODULE = 0;
 
-// If this is a shared object (MAIN_MODULE == 1 || SIDE_MODULE == 1), then we
-// will link these at runtime. They must have been built with SIDE_MODULE == 1.
-// In most cases it is simpler to pass the filenames directly on the commandline
-// instead.
+// Deprecated, list shared libraries directly on the command line instead.
 // [link]
 var RUNTIME_LINKED_LIBS = [];
 

tests/test_other.py

@@ -5430,7 +5430,8 @@ def test_RUNTIME_LINKED_LIBS(self):
     self.run_process([EMCC, '-O2', 'main.c', '-s', 'MAIN_MODULE', '-o', 'main.js', 'side.wasm'])
     self.run_js('main.js')
 
-    self.run_process([EMCC, '-O2', 'main.c', '-s', 'MAIN_MODULE', '-o', 'main2.js', '-s', 'RUNTIME_LINKED_LIBS=side.wasm'])
+    err = self.run_process([EMCC, '-O2', 'main.c', '-s', 'MAIN_MODULE', '-o', 'main2.js', '-s', 'RUNTIME_LINKED_LIBS=side.wasm'], stderr=PIPE).stderr
+    self.assertContained('emcc: warning: RUNTIME_LINKED_LIBS is deprecated', err)
     self.run_js('main2.js')
 
     self.assertBinaryEqual('main.wasm', 'main2.wasm')

tools/webassembly.py

@@ -258,58 +258,3 @@ def get_imports(wasm_file):
       assert False
 
   return imports
-
-
-def update_dylink_section(wasm_file, extra_dynlibs):
-  # A wasm shared library has a special "dylink" section, see tools-conventions repo.
-  # This function updates this section, adding extra dynamic library dependencies.
-
-  mem_size, mem_align, table_size, table_align, section_end, needed = parse_dylink_section(wasm_file)
-
-  section_name = b'\06dylink' # section name, including prefixed size
-  contents = (toLEB(mem_size) + toLEB(mem_align) +
-              toLEB(table_size) + toLEB(0))
-
-  # we extend "dylink" section with information about which shared libraries
-  # our shared library needs. This is similar to DT_NEEDED entries in ELF.
-  #
-  # In theory we could avoid doing this, since every import in wasm has
-  # "module" and "name" attributes, but currently emscripten almost always
-  # uses just "env" for "module". This way we have to embed information about
-  # required libraries for the dynamic linker somewhere, and "dylink" section
-  # seems to be the most relevant place.
-  #
-  # Binary format of the extension:
-  #
-  #   needed_dynlibs_count        varuint32       ; number of needed shared libraries
-  #   needed_dynlibs_entries      dynlib_entry*   ; repeated dynamic library entries as described below
-  #
-  # dynlib_entry:
-  #
-  #   dynlib_name_len             varuint32       ; length of dynlib_name_str in bytes
-  #   dynlib_name_str             bytes           ; name of a needed dynamic library: valid UTF-8 byte sequence
-  #
-  # a proposal has been filed to include the extension into "dylink" specification:
-  # https://github.com/WebAssembly/tool-conventions/pull/77
-  needed += extra_dynlibs
-  contents += toLEB(len(needed))
-  for dyn_needed in needed:
-    dyn_needed = dyn_needed.encode('utf-8')
-    contents += toLEB(len(dyn_needed))
-    contents += dyn_needed
-
-  orig = open(wasm_file, 'rb').read()
-  file_header = orig[:8]
-  file_remainder = orig[section_end:]
-
-  section_size = len(section_name) + len(contents)
-  with open(wasm_file, 'wb') as f:
-    # copy magic number and version
-    f.write(file_header)
-    # write the special section
-    f.write(b'\0') # user section is code 0
-    f.write(toLEB(section_size))
-    f.write(section_name)
-    f.write(contents)
-    # copy rest of binary
-    f.write(file_remainder)