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[BUG] -Wunused-result warnings in generated code #7934
Description
Describe the bug
For some functions decorated with warn_unused_result the generated C code shows warnings -Wunused-result
Cause is that the (void)(call_foo()) current pattern is not enough as generated by
cython/Cython/Compiler/Nodes.py
Line 6225 in 6ed0767
See https://godbolt.org/z/YvK6f9z6o
An alternative could be a temporary variable or for negatable return types: (void)!(call_foo())
Code to reproduce the behaviour:
from posix cimport unistd
cdef int fd
def foo():
unistd.write(fd, b"1", 1)-> Yields (void)(write(__pyx_v_fd, __pyx_k_1, 1));
Expected behaviour
Warning free code
OS
No response
Python version
No response
Cython version
No response
Additional context
No response
Activity
da-woods commentedon Aug 26, 2026
This is happening because
writeis declared with an attribute that says "this really really shouldn't be ignored". And that attribute is strong enough to bypass the(void)cast. If that's the case then surely the warning is appropriate and so Cython shouldn't go to great lengths to override it - it's a genuine error in your code and if you care enough to set-Werror=unused-resultthen you should want to see it.