Fix stringop-overread issue and quality-of-life

[joergen7]

This pr contributes a few quality-of-life improvements that I have come across. It fixes a stringop-overread warning issued by the C compiler at build, sets the minimum cmake version to a non-deprecated version, and replaces a deprecated call to distutils.

Fix stringop-overread Warning

Observation

When building pylibfst the C-compiler outputs the following warning:

In function ‘fstWritex’,
    inlined from ‘fstReaderIterBlocks2.part.0’ at /tmp/build-via-sdist-b4bq_3__/pylibfst-0.2.1.dev0/fst/fstapi.c:5903:41:
/tmp/build-via-sdist-b4bq_3__/pylibfst-0.2.1.dev0/fst/fstapi.c:3468:21: warning: ‘write’ reading between 65536 and 2147483647 bytes from a region of size 16 [-Wstringop-overread]
 3468 |                 if (write(xc->writex_fd, s, len)) { };
      |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/tmp/build-via-sdist-b4bq_3__/pylibfst-0.2.1.dev0/fst/fstapi.c: In function ‘fstReaderIterBlocks2.part.0’:
/tmp/build-via-sdist-b4bq_3__/pylibfst-0.2.1.dev0/fst/fstapi.c:5899:46: note: source object ‘vcd_id’ of size 16
 5899 |                                         char vcd_id[16];
      |                                              ^~~~~~
In file included from /usr/include/zconf.h:492,
                 from /usr/include/zlib.h:34,
                 from /tmp/build-via-sdist-b4bq_3__/pylibfst-0.2.1.dev0/fst/fstapi.h:36,
                 from /tmp/build-via-sdist-b4bq_3__/pylibfst-0.2.1.dev0/fst/fstapi.c:45:
/usr/include/unistd.h:378:16: note: in a call to function ‘write’ declared with attribute ‘access (read_only, 2, 3)’
  378 | extern ssize_t write (int __fd, const void *__buf, size_t __n) __wur
      |                ^~~~~

This is due to the function fstVcdIDForFwrite which produces id strings of unbounded size. This function is applied, however, to arrays whose size is only 16. Two bytes of such an array are reserved for delimiters. Thus, the maximum allowable size of an id string is 14.

Execution

This pr explicitly limits the size of an id string to 14, thus removing the warning.

Remove deprecated function find_executable

Observation

In the build process when setup.py is run, the Python runtime complains about the use of the function distutils.find_executable which it flags as deprecated.

<string>:20: DeprecationWarning: Use shutil.which instead of find_executable

Execution

As suggested, this pr replaces distutils.find_executable with shutil.which. Imho, it would be advisable to ditch the dependency from distutils entirely.

Fix cmake minimum version

Observation

When using contemporary distributions of cmake a warning is issued that versions before 3.10 are deprecated. I have been using cmake version 3.31.1 which ships with Alpine Linux 3.21.0.

Execution

I have set the minimum version of cmake to 3.10.

[joergen7]

Hello, I realize that one of the changes I'm proposing touches an upstream repository: gtkwave. Do you want me to revert the changes to libfst and address these with the maintainers of gtkwave instead?

[joergen7]

The improvement of setup.py remains.