cc.has_header_symbol() does not work for struct definitions

[nirbheek]

# Always succeeds
cc.has_header_symbol('linux/fs.h', 'struct file_clone_range')

# Always fails
cc.has_header_symbol('linux/fs.h', 'file_clone_range')

This is because our check evaluates to:

struct file_clone_range;

Which is just a prototype definition.

[Salamandar]

No fix yet ? I've been using it for ages without knowing it was broken.
I'm guessing the check logic itself is broken.

[Salamandar]

https://cmake.org/cmake/help/v3.0/module/CheckSymbolExists.html

If the symbol is a type or enum value it will not be recognized

CMake checks symbols ( = function, macro, variable) apart from types. Maybe Meson should do the same as it seems buggy to merge the two.

[pm215]

If I understand correctly, you can use cc.has_type() to test for the presence of "struct foo", eg

cc.has_type('struct iovec', prefix: '#include <sys/uio.h>')

Question: is there any valid use for passing a string with spaces in it to cc.has_header_symbol()? If not, would it be worth making that a syntax error or at least a warning, to catch accidental attempts to use it on "struct something" ? (The generated code for has_header_symbol() clearly doesn't envisage being passed multiple words, because it will generate "#ifndef struct foo", which is bogus syntax and provokes compiler warnings during compilation of the test case.)

(Commenting because we just fell over this with QEMU's meson.build.)

[nirbheek]

If I understand correctly, you can use cc.has_type() to test for the presence of "struct foo", eg

Yes, this issue is obsolete now. I'll close it.

If not, would it be worth making that a syntax error or at least a warning, to catch accidental attempts to use it on "struct something" ?

Absolutely, yes. Could you open a PR that does that and CC me on it?

[pm215]

I'm not sufficiently familiar with meson's internals to submit a pullreq, I'm afraid.

[eli-schwartz]

That's okay, we can offer advice. :)

You can find the compiler implementations in mesonbuild/compilers/, the base (stub) implementation which raises NotImplementedError is in compilers.py and overridden implementations for each language include for this function, c.py and cpp.py and cuda.py

Check for def has_header_symbol :D