Re: mode_t bitwise operations different under kFreeBSD?

[Petr Salinger <Petr.Salinger@seznam.cz>]

> gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -g -O2 -fPIC -g -I/usr/include/python2.7 -c src/llfuse.c -o build/temp.gnukfreebsd-8.1-1-686-smp-i686-2.7/src/llfuse.o -D_FILE_OFFSET_BITS=64 -I/usr/include/fuse -DFUSE_USE_VERSION=28 -DLLFUSE_VERSION="0.33" -Werror -Wall -Wextra -Wconversion -Wno-unused-parameter -Wno-sign-conversion -Wno-unused-but-set-variable -fno-strict-aliasing
> src/llfuse.c: In function '__pyx_f_6llfuse_fuse_mkdir':
> src/llfuse.c:4693:50: error: conversion to 'mode_t' from 'int' may alter its value [-Werror=conversion]
>
> Now, llfuse.c is itself code generated by Cython, so it's hard to read.
> However, the assignment that gcc complains about is just this:
>
> static  void __pyx_f_6llfuse_fuse_mkdir(fuse_req_t __pyx_v_req, fuse_ino_t __pyx_v_parent, const char *__pyx_v_name, mode_t __pyx_v_mode) {
>    [....]
>    __pyx_v_mode = ((__pyx_v_mode & (~S_IFMT)) | S_IFDIR);
>
>
> i.e., I'm making sure that the type bits of a mode_t variable are set to
> S_IFDIR.
>
> Why does this require a conversion in kFreeBSD?

It is roughly equal to this:

void foo(unsigned short int a)
{
   a = (( a & (~0x1F)) | 0x10);
}

This code will warn also under Linux.

Please note "unsigned short" x "signed int" and  "-Wconversion -Werror"

Petr