reassign 504699 manpages-dev severity 504699 minor thanks On Thu, Nov 06, 2008 at 11:27:01AM +0000, Paul Evans wrote: > Package: libc6 > Version: 2.7-15 > Severity: normal > > > makecontext() on AMD64 cannot pass pointer arguments to the invoked > function; they get squashed to 32bit values, ignoring the top bits. > > I'm aware that the POSIX spec doesn't require the ability to pass > pointers, though it isn't all that clear on the subject.
It is pretty clear from the POSIX specification: | Before a call is made to makecontext( ), the application shall ensure that the context being | modified has a stack allocated for it. The application shall ensure that the value of argc matches | the number of arguments of type int passed to func; otherwise, the behavior is undefined. The original POSIX specification even has "int" in bold in the text. > I've had a variety of C programmers read the makecontext(3) manpage, and > most of them didn't spot the fact it can't do pointers until I > specifically mentioned this fact. The current documentation is > insufficiently clear on the subject. > > I'd like to propose either: > > a) Extending makecontext() on AMD64 so it can pass pointers, and add a > section to the manpage to explain that you cannot portably do this, > but GNU libc happens to allow it, This is not possible, as it would break the ABI, something we do not want, and break the compliance to POSIX. > or > > b) Explain in the manpage that GNU libc cannot pass pointers. It already looks clear to me: | When this context is later activated (using setcontext(2) or swapcontext()) the function | func is called, and passed the series of integer (int) arguments that follow argc; Again the type of the argument (int) is precised. Anyway it's not a glibc bug, so I'll reassign it to manpages-dev and let the maintainer of this package either to close the bug or to precise the documentation. > Naturally I'd prefer option a because that is more useful; without the > ability to pass a pointer, it becomes much harder to actually use the > function to perform useful work in real programs, aside from the tiny > trivial examples usually given. > > > -- System Information: > Debian Release: lenny/sid > APT prefers testing > APT policy: (990, 'testing'), (500, 'unstable') > Architecture: amd64 (x86_64) > > Kernel: Linux 2.6.26-1-amd64 (SMP w/4 CPU cores) > Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8) > Shell: /bin/sh linked to /bin/bash > > Versions of packages libc6 depends on: > ii libgcc1 1:4.3.2-1 GCC support library > > libc6 recommends no packages. > > Versions of packages libc6 suggests: > pn glibc-doc <none> (no description available) > ii locales 2.7-15 GNU C Library: National Language > ( > > -- debconf information: > glibc/upgrade: true > glibc/restart-failed: > glibc/restart-services: > > > > -- > To UNSUBSCRIBE, email to [EMAIL PROTECTED] > with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED] > > -- .''`. Aurelien Jarno | GPG: 1024D/F1BCDB73 : :' : Debian developer | Electrical Engineer `. `' [EMAIL PROTECTED] | [EMAIL PROTECTED] `- people.debian.org/~aurel32 | www.aurel32.net -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
