Disallow --nominal with GC (#4758)

Nominal types don't make much sense without GC, and in particular trying to emit
them with typed function references but not GC enabled can result in invalid
binaries because nominal types do not respect the type ordering constraints
required by the typed function references proposal. Making this change was
mostly straightforward, but required fixing the fuzzer to use --nominal only
when GC is enabled and required exiting early from nominal-only optimizations
when GC was not enabled.

Fixes #4756.

1 files changed, 11 insertions, 12 deletions

diff --git a/scripts/fuzz_opt.py b/scripts/fuzz_opt.py
index 745065732..01895c585 100755
--- a/scripts/fuzz_opt.py
+++ b/scripts/fuzz_opt.py
@@ -39,7 +39,6 @@ TYPE_SYSTEM_FLAG = '--nominal'
 
 # feature options that are always passed to the tools.
 CONSTANT_FEATURE_OPTS = ['--all-features']
-CONSTANT_FEATURE_OPTS.append(TYPE_SYSTEM_FLAG)
 
 INPUT_SIZE_MIN = 1024
 INPUT_SIZE_MEAN = 40 * 1024
@@ -120,6 +119,9 @@ def randomize_feature_opts():
                 if possible in IMPLIED_FEATURE_OPTS:
                     FEATURE_OPTS.extend(IMPLIED_FEATURE_OPTS[possible])
     print('randomized feature opts:', '\n  ' + '\n  '.join(FEATURE_OPTS))
+    # Type system flags only make sense when GC is enabled
+    if '--disable-gc' not in FEATURE_OPTS:
+        FEATURE_OPTS.append(TYPE_SYSTEM_FLAG)
 
 
 ALL_FEATURE_OPTS = ['--all-features', '-all', '--mvp-features', '-mvp']
@@ -819,8 +821,8 @@ class CheckDeterminism(TestCaseHandler):
         b1 = open('b1.wasm', 'rb').read()
         b2 = open('b2.wasm', 'rb').read()
         if (b1 != b2):
-            run([in_bin('wasm-dis'), 'b1.wasm', '-o', 'b1.wat', TYPE_SYSTEM_FLAG])
-            run([in_bin('wasm-dis'), 'b2.wasm', '-o', 'b2.wat', TYPE_SYSTEM_FLAG])
+            run([in_bin('wasm-dis'), 'b1.wasm', '-o', 'b1.wat', FEATURE_OPTS])
+            run([in_bin('wasm-dis'), 'b2.wasm', '-o', 'b2.wat', FEATURE_OPTS])
             t1 = open('b1.wat', 'r').read()
             t2 = open('b2.wat', 'r').read()
             compare(t1, t2, 'Output must be deterministic.', verbose=False)
@@ -1379,10 +1381,8 @@ on valid wasm files.)
                 with open('reduce.sh', 'w') as reduce_sh:
                     reduce_sh.write('''\
 # check the input is even a valid wasm file
-echo "At least one of the next two values should be 0:"
-%(wasm_opt)s %(typesystem)s --detect-features %(temp_wasm)s
-echo "  " $?
-%(wasm_opt)s %(typesystem)s --all-features %(temp_wasm)s
+echo "The following value should be 0:"
+%(wasm_opt)s %(features)s %(temp_wasm)s
 echo "  " $?
 
 # run the command
@@ -1419,7 +1419,7 @@ echo "  " $?
                          'auto_init': auto_init,
                          'original_wasm': original_wasm,
                          'temp_wasm': os.path.abspath('t.wasm'),
-                         'typesystem': TYPE_SYSTEM_FLAG,
+                         'features': ' '.join(FEATURE_OPTS),
                          'reduce_sh': os.path.abspath('reduce.sh')})
 
                 print('''\
@@ -1441,7 +1441,7 @@ You can reduce the testcase by running this now:
 vvvv
 
 
-%(wasm_reduce)s %(type_system_flag)s %(original_wasm)s '--command=bash %(reduce_sh)s' -t %(temp_wasm)s -w %(working_wasm)s
+%(wasm_reduce)s %(features)s %(original_wasm)s '--command=bash %(reduce_sh)s' -t %(temp_wasm)s -w %(working_wasm)s
 
 
 ^^^^
@@ -1449,9 +1449,8 @@ vvvv
 
 Make sure to verify by eye that the output says something like this:
 
-At least one of the next two values should be 0:
+The following value should be 0:
   0
-  1
 The following value should be 1:
   1
 
@@ -1471,7 +1470,7 @@ After reduction, the reduced file will be in %(working_wasm)s
                        'working_wasm': os.path.abspath('w.wasm'),
                        'wasm_reduce': in_bin('wasm-reduce'),
                        'reduce_sh': os.path.abspath('reduce.sh'),
-                       'type_system_flag': TYPE_SYSTEM_FLAG})
+                       'features': ' '.join(FEATURE_OPTS)})
                 break
         if given_seed is not None:
             break