emscripten-core/emscripten

preamble.js: emcc-generated functions have length 0

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#14,554 opened on Jun 29, 2021

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help wanted

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Description

echo >test.c 'int foo (int x) { return 0; }
' &&
echo >test.js 'assert (
_foo .length == 01,
[ '\''foo has'\'',
_foo .length,
'\''arguments'\''
] .join ('\'' '\''
))' &&
emcc test.c --post-js test.js -sEXPORTED_FUNCTIONS=_foo &&
node a.out

Assertion failed: foo has 0 arguments

Contributor guide

Research direction
Inspect how emcc generates exported function wrappers in the compiled JavaScript and why the .length property of the exported function is zero. Trace the code path in preamble.js that sets the length of generated functions.
Tech stack
cjavascript
Domain
tooling
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
CJavaScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30