fix(wasm): enable C++ exception catching in the Emscripten build - #136
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Emscripten disables exception catching by default, so throws abort and catch blocks are elided. nec_context uses `throw 1` to unwind a finished solve, and nec_process_input relies on catching nec_exception to report errors. Pass -fexceptions at both compile and link time. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The CI wasm job only checked that nec2pp.js/nec2pp.wasm were produced. Load the module under Node, feed nec_process_input a deck that makes the geometry parser throw, and require rc -2 with the error in the output. Without exception catching the throw escapes into JS and the test fails. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This was referenced Oct 2, 2026
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tmolteno/necpp#129 was closed as superseded by d0f3259 upstream. The -fexceptions fix for NECPP_BUILD_WASM went up as tmolteno/necpp#136 and was withdrawn: that target is a stub, and build.sh already passes the flag. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Uri4eguGitqE1abazuTstd
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Summary
Emscripten disables C++ exception catching by default: a
throwaborts the module andcatchblocks are dropped. TheNECPP_BUILD_WASMtarget didn't pass-fexceptions, so this adds it to both the compile and link options ofnec2pp_wasm. It has to be a compile flag too; the link flag alone can't restore acatchthat was already dropped from the objects.Two places depend on it:
nec_context::simulateusesthrow 1/catch (int)to end a finished run and return to card input (src/nec_context.cpp).nec_process_inputinsrc/nec_wasm.cppcatchesnec_exceptionso it can return-2with the error message.nec_process_inputis still a stub that parses geometry from stdin and never callssimulate(), so today only the error path is reachable from the WASM API.Also adds
tests/wasm_smoke.js, which runs in the CIwasmjob. Until now that job only checked thatnec2pp.jsandnec2pp.wasmwere produced, and the build succeeds with or without exception support. The test loads the module under Node, givesnec_process_inputempty stdin so the geometry parser throws, and requires rc-2with the error message in the output.Test plan
node tests/wasm_smoke.js nec2pp.jspasses against a build of this branch (emscripten/emsdk:4.0.7, viascripts/build_wasm_docker.sh)wasmjob passes🤖 Generated with Claude Code
https://claude.ai/code/session_01Uri4eguGitqE1abazuTstd