default -Wl,--allow-multiple-definition to on

var/spack/repos/builtin/packages/ffmpeg/package.py

@@ -61,7 +61,7 @@ class Ffmpeg(AutotoolsPackage):
     #         description='XML parsing, needed for dash demuxing support')
     variant('libzmq', default=False, description='message passing via libzmq')
     variant('lzma', default=False, description='lzma support')
-    variant('avresample', default=False, description='AV reasmpling component')
+    variant('avresample', default=False, description='AV resampling component (deprecated)')
     variant('openssl', default=False, description='needed for https support')
     variant('sdl2', default=False, description='sdl2 support')
     variant('shared', default=True, description='build shared libraries')
@@ -132,15 +132,6 @@ def enable_or_disable_meta(self, variant, options):
         switch = 'enable' if '+{0}'.format(variant) in self.spec else 'disable'
         return ['--{0}-{1}'.format(switch, option) for option in options]
 
-    def flag_handler(self, name, flags):
-        if self.spec.satisfies('%emscripten'):
-            if name == 'ldflags':
-                # This is a patch to LLVM which only works if
-                # "llvm+multiple-definitions" is enabled.
-                flags.append('{}--allow-multiple-definition'
-                             .format(self.compiler.linker_arg))
-        return (flags, None, None)
-
     patch('disable-asm.patch', when='%emscripten')
 
     def configure_args(self):

var/spack/repos/builtin/packages/llvm/multiple-definitions-wasm.patch

@@ -11,29 +11,16 @@ index 8eaa4acc6..abaf1c9a2 100644
    bool demangle;
    bool disableVerify;
 diff --git a/lld/wasm/Driver.cpp b/lld/wasm/Driver.cpp
-index 1dc6b9dd6..79685b24a 100644
+index 1dc6b9dd6..68826b567 100644
 --- a/lld/wasm/Driver.cpp
 +++ b/lld/wasm/Driver.cpp
-@@ -345,11 +345,22 @@ static UnresolvedPolicy getUnresolvedSymbolPolicy(opt::InputArgList &args) {
-   return errorOrWarn;
- }
- 
-+static bool hasZOption(opt::InputArgList &args, StringRef key) {
-+  for (auto *arg : args.filtered(OPT_z))
-+    if (key == arg->getValue())
-+      return true;
-+  return false;
-+}
-+
- // Initializes Config members by the command line options.
- static void readConfigs(opt::InputArgList &args) {
+@@ -350,6 +350,9 @@ static void readConfigs(opt::InputArgList &args) {
    config->bsymbolic = args.hasArg(OPT_Bsymbolic);
    config->checkFeatures =
        args.hasFlag(OPT_check_features, OPT_no_check_features, true);
 +  config->allowMultipleDefinition =
 +      args.hasFlag(OPT_allow_multiple_definition,
-+                   OPT_no_allow_multiple_definition, false) ||
-+      hasZOption(args, "muldefs");
++                   OPT_no_allow_multiple_definition, true);
    config->compressRelocations = args.hasArg(OPT_compress_relocations);
    config->demangle = args.hasFlag(OPT_demangle, OPT_no_demangle, true);
    config->disableVerify = args.hasArg(OPT_disable_verify);

var/spack/repos/builtin/packages/llvm/package.py

@@ -375,7 +375,9 @@ class Llvm(CMakePackage, CudaPackage):
     # patch for missing hwloc.h include for libompd
     patch('llvm14-hwloc-ompd.patch', when='@14')
 
-    # Allow wasm-ld to have a --allow-multiple-definition or -z muldefs flag.
+    # Allow wasm-ld to have a --allow-multiple-definition flag, turned on by
+    # default. This mirrors the behavior of gcc when producing and consuming
+    # shared libraries.
     patch('multiple-definitions-wasm.patch', when='+multiple-definitions')
 
     # The functions and attributes below implement external package