[Fortran] Failing test fortranlib_test_F03 on big-endian 32-bit architectures with 64-bit time_t size

[pini-gh]

Describe the bug
Debian has recently had a transition to 64-bit time_t size in order to avoid the year 2038 bug. See https://wiki.debian.org/ReleaseGoals/64bit-time.

Since then the fortranlib_test_F03 test has been failing on big-endian 32-bit architectures with:

Testing object functions                                                               PASSED
 h5ovisit_f FAILED
 h5ovisit_f FAILED
 h5ovisit_f FAILED
 h5ovisit_f FAILED
 h5ovisit_by_name_f FAILED
 h5ovisit_by_name_f FAILED
 Testing object visiting functions                                                     *FAILED*

See e.g. https://buildd.debian.org/status/fetch.php?pkg=hdf5&arch=hppa&ver=1.14.5%2Brepack-2&stamp=1735623616&raw=0.

It appears that this failure is caused by the fortran function h5gmtime() always returning 01/01/1970.

On 32-bit architectures, when time_t size is set to 64-bit, h5gmtime() must call C function __gmtime64() instead of gmtime() which is for 32-bit time_t only.

The fact that it affects big-endian 32-bit architectures only is because on little-endian the lower 32 bits of the 64-bit time_t value are stored in the first 4 bytes (and thus have the correct value).

Expected behavior
Successful test.

Platform (please complete the following information)

• HDF5 version 1.14.5
• OS and version Debian unstable on hppa or powerpc
• Compiler and version gcc / gfortran 14.2.0
• Build system (e.g. CMake, Autotools) autotools
• Any configure options you specified --enable-fortran --enable-fortran2003 --enable-tests
• MPI library and version (parallel HDF5) unrelevant

Patch proposal
Please find attached a patch proposal which should work for both autotools and cmake build systems.

fortran_gmtime64.patch.gz