Upgrade to emsdk v3.1.48 breaking build

[oboukli]

This popped up in v3.1.48

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.48 (e967e20b4727956a30592165a3c1cde5c67fa0a8)
clang version 18.0.0 (https://github.com/llvm/llvm-project a54545ba6514802178cf7cf1c1dd9f7efbf3cde7)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /emsdk/upstream/bin

Failing command line in full:

main.c

int main() {}

emcc -Wall -Werror \
--closure 1 \
-s ASSERTIONS=0 \
-s ASYNCIFY \
-s STRICT \
main.c \
-o main.js

building:ERROR: Closure compiler run failed:

building:ERROR: /tmp/emscripten_temp_pxv1nuis/main.js:927:20: ERROR - [JSC_UNDEFINED_VARIABLE] variable assert is undeclared
  927|                     assert(y === x);
                           ^^^^^^

1 error(s), 0 warning(s)

emcc: error: closure compiler failed (rc: 1): /emsdk/node/16.20.0_64bit/bin/node --max_old_space_size=8192 /emsdk/upstream/emscripten/node_modules/.bin/google-closure-compiler --compilation_level ADVANCED_OPTIMIZATIONS --language_in ECMASCRIPT_2021 --language_out NO_TRANSPILE --emit_use_strict=false --externs /emsdk/upstream/emscripten/src/closure-externs/closure-externs.js --externs /emsdk/upstream/emscripten/src/closure-externs/node-externs.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/buffer.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/string_decoder.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/os.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/tty.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/domain.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/process.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/readline.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/path.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/vm.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/dgram.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/events.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/util.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/dns.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/zlib.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/punycode.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/url.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/cluster.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/stream.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/repl.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/child_process.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/https.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/querystring.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/net.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/tls.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/fs.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/http.js --externs /emsdk/upstream/emscripten/third_party/closure-compiler/node-externs/core.js --externs /emsdk/upstream/emscripten/src/closure-externs/dyncall-externs.js --js /tmp/emscripten_temp_pxv1nuis/main.js --js_output_file tmp1jccdo1f.cc.js --formatting PRETTY_PRINT

[sbc100]

Looks like you fell afoul of #20592. With this change, when you enable STRICT mode we only define assert in debug builds.

It looks like we don't find all the places in the standard library that use assert with being guarded with #if ASSERTIONS. This one looks like its in src/library_async.js. WE can fix that, but for quick workaround you could temporarily remove -sSTRICT

[oboukli]

Removed -s ASSERTIONS=0 from the command-line above and the build succeeded, while retaining -s STRICT.

I'm afraid #if ASSERTIONS is evaluating to true when ASSERTIONS=0. Probably the #if ASSERTIONS guards need to be changed to #if ASSERTIONS == 1

[sbc100]

Removed -s ASSERTIONS=0 from the command-line above and the build succeeded, while retaining -s STRICT.

I'm afraid #if ASSERTIONS is evaluating to true when ASSERTIONS=0. Probably the #if ASSERTIONS guards need to be changed to #if ASSERTIONS == 1

No, #if ASSERTIONS block will not be included when -sASSERTIONS=0. This is very well tested.

You shouldn't need to change anything about -sASSERTIONS, its only the -sSTRICT that you will have to remove until the fix lands. When STRICT is not used you should have no problem at all.

[sbc100]

The reason removing -s ASSERTIONS=0 worked for you is that when you build without optimizations ASSERTIONS defaults to 1 so the problem doesn't manifest. The bug will only manifest when you combine ASSERTIONS=0 (or equivalently optimizations e.g. -O2) with STRICT.