Using CLAPACK (Fortran-to-C autoconverted code) in emscripten?

[nickw]

Hi,

I am investigating using Emscripten to provide a web interface to an augmented reality system,. PTAM (https://www.robots.ox.ac.uk/~gk/PTAM/)

I have written a small test application which just initialises the library. At the link stage I get this error:

```

[ 50%] Linking CXX executable ptam_wasm.js
[parse exception: attempted pop from empty stack / beyond block start boundary at 122228 (at 0:122228)]
Fatal: error in parsing input
em++: error: '/home/nick/src/emsdk/upstream/bin/wasm-emscripten-finalize --minimize-wasm-changes --dyncalls-i64 ptam_wasm.wasm -o ptam_wasm.wasm --detect-features' failed (returned 1)
CMakeFiles/ptam_wasm.dir/build.make:112: recipe for target 'ptam_wasm.js' failed
make[2]: *** [ptam_wasm.js] Error 1
CMakeFiles/Makefile2:67: recipe for target 'CMakeFiles/ptam_wasm.dir/all' failed
make[1]: *** [CMakeFiles/ptam_wasm.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2
emmake: error: 'make' failed (returned 2)
```

This error appears to have been reported occasionally at other times, but without a definite cause other than Emscripten trying to deal with code which it cannot process.

Doing a bit of analysis to locate the problem by commenting out the PTAM code until I find a call which produces the error when uncommented and not when commented, I find that a function in the CLAPACK library (C conversion of maths library LAPACK) is the source of the problem.

CLAPACK is C code auto-generated from Fortran (http://www.netlib.org/clapack/)

Looking at the code, it seems somewhat non-standard in style, being autogenerated by `f2c`.

Does emscripten have a known problem with this type of code? Has anyone else tried using emscripten with CLAPACK?

Thanks,

Nick

[nickw]

To follow up on this and give a little more info, the function causing the problem in CLAPACK is the dgesvd_() function within file dgesvd.c

Unusual (to my eyes) coding styles from this auto-generated code include function declarations within the body of another function, something I have not encountered before.

[nickw]

Sorted this in the end.. digging a bit deeper revealed the problem eventually, in the CLAPACK library some function declarations returned int when the implenentation (in the f2c library) had them returning void.