|author||Rich Felker <firstname.lastname@example.org>||2014-03-07 23:56:48 -0500|
|committer||Rich Felker <email@example.com>||2014-03-07 23:56:48 -0500|
in fcntl, use unsigned long instead of long for variadic argument type
neither is correct; different commands take different argument types, and some take no arguments at all. I have a much larger overhaul of fcntl prepared to address this, but it's not appropriate to commit during freeze. the immediate problem being addressed affects forward-compatibility on x32: if new commands are added and they take pointers, but the libc-level fcntl function is not aware of them, using long would sign-extend the pointer to 64 bits and give the kernel an invalid pointer. on the kernel side, the argument to fcntl is always treated as unsigned long, so no harm is done by treating possibly-signed integer arguments as unsigned. for every command that takes an integer argument except for F_SETOWN, large integer arguments and negative arguments are handled identically anyway. in the case of F_SETOWN, the kernel is responsible for converting the argument which it received as unsigned long to int, so the sign of negative arguments is recovered. the other problem that will be addressed later is that the type passed to va_arg does not match the type in the caller of fcntl. an advanced compiler doing cross-translation-unit analysis could potentially see this mismatch and issue warnings or otherwise make trouble. on i386, this patch was confirmed not to alter the code generated by gcc 4.7.3. in principle the generated code should not be affected on any arch except x32.
Diffstat (limited to 'arch')
0 files changed, 0 insertions, 0 deletions