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The only difference between noncompliant and C99-compliant scanf is that the former accepts the archaic GNU extension '%as' (also %aS and %a[...]) meaning to allocate space for the input string with malloc. This extension conflicts with C99's use of %a as a format _type_ meaning to read a floating-point number; POSIX.1-2008 standardized equivalent functionality using the modifier letter 'm' instead (%ms, %mS, %m[...]). The extension was already disabled in most conformance modes: specifically, any mode that doesn't involve _GNU_SOURCE and _does_ involve either strict conformance to C99 or loose conformance to both C99 and POSIX.1-2001 would get the C99-compliant scanf. With compilers new enough to use -std=gnu11 instead of -std=gnu89, or equivalent, that includes the default mode. With this patch, we now provide C99-compliant scanf in all configurations except when _GNU_SOURCE is defined *and* __STDC_VERSION__ or __cplusplus (whichever is relevant) indicates C89/C++98. This leaves the old scanf available under e.g. -std=c89 -D_GNU_SOURCE, but removes it from e.g. -std=gnu11 -D_GNU_SOURCE (it was already not present under -std=gnu11 without -D_GNU_SOURCE) and from -std=gnu89 without -D_GNU_SOURCE. There needs to be an internal override so we can compile the noncompliant scanf itself. This is the same problem we had when we removed 'gets' from _GNU_SOURCE and it's dealt with the same way: there's a new __GLIBC_USE symbol, DEPRECATED_SCANF, which defaults to off under the appropriate conditions for external code, but can be overridden by individual files within stdio. We also run into problems with PLT bypass for internal uses of sscanf, because libc_hidden_proto uses __REDIRECT and so does the logic in stdio.h for choosing which implementation of scanf to use; __REDIRECT isn't transitive, so include/stdio.h needs to bridge the gap with a macro. As far as I can tell, sscanf is the only function in this family that's internally called by unrelated code. Finally, there are several tests in stdio-common that use the extension. bug21.c is a regression test for a crash; it still exercises the relevant code when changed to use %ms instead of %as. scanf14.c through scanf17.c are more complicated since they are actually testing the subtleties of the extension - under what circumstances is 'a' treated as a modifier letter, etc. I changed all of them to use %ms instead of %as as well, but duplicated scanf14.c and scanf16.c as scanf14a.c and scanf16a.c. These still use %as and are compiled with -std=gnu89 to access the old extension. A bunch of diagnostic overrides and manual workarounds for the old stdio.h behavior become unnecessary. Yay! * include/features.h (__GLIBC_USE_DEPRECATED_SCANF): New __GLIBC_USE parameter. Only use deprecated scanf when __USE_GNU is defined and __STDC_VERSION__ is less than 199901L or __cplusplus is less than 201103L, whichever is relevant for the language being compiled. * libio/stdio.h, libio/bits/stdio-ldbl.h: Decide whether to redirect scanf, fscanf, sscanf, vscanf, vfscanf, and vsscanf to their __isoc99_ variants based only on __GLIBC_USE (DEPRECATED_SCANF). * wcsmbs/wchar.h: wcsmbs/bits/wchar-ldbl.h: Likewise for wscanf, fwscanf, swscanf, vwscanf, vfwscanf, and vswscanf. * libio/iovsscanf.c * libio/fwscanf.c * libio/iovswscanf.c * libio/swscanf.c * libio/vscanf.c * libio/vwscanf.c * libio/wscanf.c * stdio-common/fscanf.c * stdio-common/scanf.c * stdio-common/vfscanf.c * stdio-common/vfwscanf.c * sysdeps/ieee754/ldbl-opt/nldbl-compat.c * sysdeps/ieee754/ldbl-opt/nldbl-fscanf.c * sysdeps/ieee754/ldbl-opt/nldbl-fwscanf.c * sysdeps/ieee754/ldbl-opt/nldbl-iovfscanf.c * sysdeps/ieee754/ldbl-opt/nldbl-scanf.c * sysdeps/ieee754/ldbl-opt/nldbl-sscanf.c * sysdeps/ieee754/ldbl-opt/nldbl-swscanf.c * sysdeps/ieee754/ldbl-opt/nldbl-vfscanf.c * sysdeps/ieee754/ldbl-opt/nldbl-vfwscanf.c * sysdeps/ieee754/ldbl-opt/nldbl-vscanf.c * sysdeps/ieee754/ldbl-opt/nldbl-vsscanf.c * sysdeps/ieee754/ldbl-opt/nldbl-vswscanf.c * sysdeps/ieee754/ldbl-opt/nldbl-vwscanf.c * sysdeps/ieee754/ldbl-opt/nldbl-wscanf.c: Override __GLIBC_USE_DEPRECATED_SCANF to 1. * stdio-common/sscanf.c: Likewise. Remove ldbl_hidden_def for __sscanf. * stdio-common/isoc99_sscanf.c: Add libc_hidden_def for __isoc99_sscanf. * include/stdio.h: Provide libc_hidden_proto for __isoc99_sscanf, not sscanf. [!__GLIBC_USE (DEPRECATED_SCANF)]: Define sscanf as __isoc99_scanf with a preprocessor macro. * stdio-common/bug21.c, stdio-common/scanf14.c: Use %ms instead of %as, %mS instead of %aS, %m[] instead of %a[]; remove DIAG_IGNORE_NEEDS_COMMENT for -Wformat. * stdio-common/scanf16.c: Likewise. Add __attribute__ ((format (scanf))) to xscanf, xfscanf, xsscanf. * stdio-common/scanf14a.c: New copy of scanf14.c which still uses %as, %aS, %a[]. Remove DIAG_IGNORE_NEEDS_COMMENT for -Wformat. * stdio-common/scanf16a.c: New copy of scanf16.c which still uses %as, %aS, %a[]. Add __attribute__ ((format (scanf))) to xscanf, xfscanf, xsscanf. * stdio-common/scanf15.c, stdio-common/scanf17.c: No need to override feature selection macros or provide definitions of u_char etc. * stdio-common/Makefile (tests): Add scanf14a and scanf16a. (CFLAGS-scanf15.c, CFLAGS-scanf17.c): Remove. (CFLAGS-scanf14a.c, CFLAGS-scanf16a.c): New. Compile these files with -std=gnu89. |
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| COPYING | ||
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| INSTALL | ||
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| version.h | ||
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. When working with Linux kernels, this version of the GNU C Library requires Linux kernel version 3.2 or later. 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 csky-*-linux-gnuabiv2 hppa-*-linux-gnu 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 riscv64-*-linux-gnu sh[34]-*-linux-gnu sparc*-*-linux-gnu sparc64*-*-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.