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getopt can print a whole bunch of error messages, and when used standalone (from gnulib) it uses fprintf to do that. But fprintf is a cancellation point and getopt isn't, and also applying fprintf to a stream in wide-character mode is not allowed. glibc has an internal function called __fxprintf that writes a narrow format string to a stream regardless of mode, but it only handles ASCII format strings, and it's still a cancellation point. getopt's messages are translated, so they might not be ASCII. So getopt has an error message to an asprintf buffer, monkeys with internal flag bits on stderr to disable cancellation, and then calls __fxprintf(stderr, "%s", buffer). There isn't even a helper function, the code is duplicated every time. This patch fixes __fxprintf to handle arbitrary multibyte format strings, and adds a variant __fxprintf_nocancel that does the same thing but also isn't a cancellation point. (It still _works_ by monkeying with internal flag bits on the FILE, but that's not really a layering violation for code in stdio-common.) All of the #ifdef _LIBC blocks can then be reduced to their standalone versions with a little help from some macros at the top of the file. I also wrote a test case to verify that getopt really isn't a cancellation point, and I'm glad I did, because it found two bugs, one of which wasn't even to do with cancellation (see previous patch). * stdio-common/fxprintf.c (__fxprintf_nocancel): New function. (locked_vfxprintf): New helper function. Handle arbitrary multibyte strings, not just ASCII. * include/stdio.h: Declare __fxprintf_nocancel. * posix/getopt.c: When _LIBC is defined, define fprintf to __fxprintf_nocancel, flockfile to _IO_flockfile, and funlockfile to _IO_funlockfile. When neither _LIBC nor _POSIX_THREAD_SAFE_FUNCTIONS is defined, define flockfile and funlockfile as no-ops. (_getopt_internal_r): Remove all internal #ifdef _LIBC blocks; the standalone error-printing code can now be used for libc as well. Add an flockfile/funlockfile pair around one case where the error message is printed in several chunks. Don't use fputc. * posix/tst-getopt-cancel.c: New test. * posix/Makefile: Run it. |
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| WUR-REPORT | ||
This directory contains the sources of the GNU C Library. See the file "version.h" for what release version you have. The GNU C Library is the standard system C library for all GNU systems, and is an important part of what makes up a GNU system. It provides the system API for all programs written in C and C-compatible languages such as C++ and Objective C; the runtime facilities of other programming languages use the C library to access the underlying operating system. In GNU/Linux systems, the C library works with the Linux kernel to implement the operating system behavior seen by user applications. In GNU/Hurd systems, it works with a microkernel and Hurd servers. The GNU C Library implements much of the POSIX.1 functionality in the GNU/Hurd system, using configurations i[4567]86-*-gnu. The current GNU/Hurd support requires out-of-tree patches that will eventually be incorporated into an official GNU C Library release. When working with Linux kernels, this version of the GNU C Library requires Linux kernel version 3.2 or later on all architectures except i[4567]86 and x86_64, where Linux kernel version 2.6.32 or later suffices. Also note that the shared version of the libgcc_s library must be installed for the pthread library to work correctly. The GNU C Library supports these configurations for using Linux kernels: aarch64*-*-linux-gnu alpha*-*-linux-gnu arm-*-linux-gnueabi hppa-*-linux-gnu Not currently functional without patches. i[4567]86-*-linux-gnu x86_64-*-linux-gnu Can build either x86_64 or x32 ia64-*-linux-gnu m68k-*-linux-gnu microblaze*-*-linux-gnu mips-*-linux-gnu mips64-*-linux-gnu powerpc-*-linux-gnu Hardware or software floating point, BE only. powerpc64*-*-linux-gnu Big-endian and little-endian. s390-*-linux-gnu s390x-*-linux-gnu sh[34]-*-linux-gnu sparc*-*-linux-gnu sparc64*-*-linux-gnu tilegx-*-linux-gnu tilepro-*-linux-gnu If you are interested in doing a port, please contact the glibc maintainers; see http://www.gnu.org/software/libc/ for more information. See the file INSTALL to find out how to configure, build, and install the GNU C Library. You might also consider reading the WWW pages for the C library at http://www.gnu.org/software/libc/. The GNU C Library is (almost) completely documented by the Texinfo manual found in the `manual/' subdirectory. The manual is still being updated and contains some known errors and omissions; we regret that we do not have the resources to work on the manual as much as we would like. For corrections to the manual, please file a bug in the `manual' component, following the bug-reporting instructions below. Please be sure to check the manual in the current development sources to see if your problem has already been corrected. Please see http://www.gnu.org/software/libc/bugs.html for bug reporting information. We are now using the Bugzilla system to track all bug reports. This web page gives detailed information on how to report bugs properly. The GNU C Library is free software. See the file COPYING.LIB for copying conditions, and LICENSES for notices about a few contributions that require these additional notices to be distributed. License copyright years may be listed using range notation, e.g., 1996-2015, indicating that every year in the range, inclusive, is a copyrightable year that would otherwise be listed individually.