Use of FE_INVALID breaks WebAssembly builds of HDF5 1.14.5

[LTLA]

Describe the bug

HDF5 1.14.5 cannot compile to WebAssembly as Emscripten does not support the FE_* macros.

Expected behavior

The compilation should succeed.

Platform (please complete the following information)

• HDF5 1.14.5.
• Ubuntu 22.04.5 LTS
• Emscripten 3.1.68
• Cmake
• Multiple configure flags (see below)
• No MPI

Additional context

Emscripten fails on the following chunk of code:

hdf5/src/H5Tinit_float.c

Lines 611 to 613 in 6b43197

	/* Clear any FE_INVALID exceptions from NaN handling */
	if (feclearexcept(FE_INVALID) != 0)
	HSYS_GOTO_ERROR(H5E_DATATYPE, H5E_CANTSET, FAIL, "can't clear floating-point exceptions");

with:

# ... skipping Cmake logs...
[ 78%] Building C object src/CMakeFiles/hdf5-static.dir/H5Tinit_float.c.o
/home/luna/Code/js/scran.js/extern/hdf5/demo/hdf5-1.14.5/src/H5Tinit_float.c:612:23: error: use of undeclared identifier 'FE_INVALID'
  612 |     if (feclearexcept(FE_INVALID) != 0)
      |                       ^
1 error generated.

This is because many of the FE_* macros are not defined by Emscripten (emscripten-core/emscripten#13678). While I'm not familiar with the intricacies of the C standard, some reading suggests that compliant implementations do not need to define these macros.

Currently I'm modifying the HDF5 source code directly so that the compilation can complete. Would you consider adding an #ifdef FE_INVALID around this block so that it compiles out of the box?

FWIW the MRE is:

# Unzip the downloaded tarball.
tar -xf hdf5-1.14.5.tar.gz

# Avoid problems from a random package.json in a parent directory.
echo "{}" > package.json 

# Assumes you have Emscripten installed, I'm using 3.1.68. Also
# I'm using Cmake 3.27.1, but I don't think it really matters.
emcmake cmake \
    -S hdf5-1.14.5 \
    -B build-1.14.5 \
    -DCMAKE_BUILD_TYPE=Release \
    -DCMAKE_INSTALL_PREFIX=installed \
    -DBUILD_SHARED_LIBS=OFF \
    -DBUILD_TESTING=OFF \
    -DHDF5_BUILD_EXAMPLES=OFF \
    -DHDF5_BUILD_TOOLS=OFF \
    -DHDF5_BUILD_UTILS=OFF \
    -DHDF5_BUILD_CPP_LIB=ON \
    -DHDF5_ENABLE_Z_LIB_SUPPORT=ON \
    -DZLIB_USE_EXTERNAL=OFF \
    -DHDF5_ENABLE_SZIP_SUPPORT=OFF

# Reproduces the error.
cd build-1.14.5
emmake make

[bmaranville]

This is also the only usage of an FE_XX macro in the whole HDF5 codebase, as far as I can tell.

[derobins]

I think the suggested fix (an #ifdef FE_INVALID block around the error check/clear) is a valid solution.