glibc/libio/bits, branch master

Use a doubly-linked list for _IO_list_all (bug 27777)

2024-05-17T21:13:25Z

This patch fixes BZ #27777 "fclose does a linear search, takes ages when many FILE* are opened". Simply put, the master list of opened (FILE*), namely _IO_list_all, is a singly-linked list. As a consequence, the removal of a single element is in O(N), which cripples the performance of fclose(). The patch switches to a doubly-linked list, yielding O(1) removal. The one padding field in struct _IO_FILE, __pad5, is renamed to _prevchain for a doubly-linked list. Since fields in struct _IO_FILE after the _lock field are internal to glibc and opaque to applications. We can change them as long as the size of struct _IO_FILE is unchanged, which is checked as the part of glibc ABI with sizes of _IO_2_1_stdin_, _IO_2_1_stdout_ and _IO_2_1_stderr_. NB: When _IO_vtable_offset (fp) == 0, copy relocation will cover the whole struct _IO_FILE. Otherwise, only fields up to the _lock field will be copied to applications at run-time. It is used to check if the _prevchain field can be safely accessed. After opening 2 million (FILE*), the fclose() of 100 of them takes quite a few seconds without the patch, and under 2 seconds with it on a loaded machine. No test is added since there are no functional changes. Co-Authored-By: H.J. Lu Signed-off-by: Alexandre Ferrieux Signed-off-by: H.J. Lu Reviewed-by: Carlos O'Donell

libio: Improve fortify with clang

2024-02-27T13:52:58Z

It improve fortify checks for sprintf, vsprintf, vsnsprintf, fprintf, dprintf, asprintf, __asprintf, obstack_printf, gets, fgets, fgets_unlocked, fread, and fread_unlocked. The runtime checks have similar support coverage as with GCC. For function with variadic argument (sprintf, snprintf, fprintf, printf, dprintf, asprintf, __asprintf, obstack_printf) the fortify wrapper calls the va_arg version since clang does not support __va_arg_pack. Checked on aarch64, armhf, x86_64, and i686. Reviewed-by: Carlos O'Donell Tested-by: Carlos O'Donell

Refer to C23 in place of C2X in glibc

2024-02-01T11:02:01Z

WG14 decided to use the name C23 as the informal name of the next revision of the C standard (notwithstanding the publication date in 2024). Update references to C2X in glibc to use the C23 name. This is intended to update everything *except* where it involves renaming files (the changes involving renaming tests are intended to be done separately). In the case of the _ISOC2X_SOURCE feature test macro - the only user-visible interface involved - support for that macro is kept for backwards compatibility, while adding _ISOC23_SOURCE. Tested for x86_64.

Update copyright dates with scripts/update-copyrights

2024-01-01T18:53:40Z

libio: Add nonnull attribute for most FILE * arguments in stdio.h

2023-09-27T00:11:38Z

During the review of a GCC analyzer test case, we found most stdio functions accepting a FILE * argument expect it to be nonnull and just segfault when the argument is NULL. Add nonnull attribute for them. fflush and fflush_unlocked are well defined when __stream is NULL so they are not touched. For fputs, fgets, fread, fwrite, fprintf, vfprintf, and their unlocked version, if __stream is empty but there is nothing to read or write, they did not segfault. But the standard disallow __stream to be empty here, so nonnull attribute is also added for them. Note that this may blow up some old code already subtly broken. Also add __nonnull for _chk variants and __fortify_function versions for them. Signed-off-by: Xi Ruoyao Reviewed-by: Alejandro Colomar Reviewed-by: Siddhesh Poyarekar

libio/bits/stdio2-decl.h: Avoid PLT entries with _FORTIFY_SOURCE

2023-07-05T14:59:48Z

The change is meant to avoid unwanted PLT entry for the fgets_unlocked routine when _FORTIFY_SOURCE is set. Reviewed-by: Siddhesh Poyarekar

libio/bits/stdio2.h: Clearly separate declaration from definitions

2023-07-05T14:59:48Z

Move declarations from libio/bits/stdio.h to existing libio/bits/stdio2-decl.h. This will enable future use of __REDIRECT_FORTIFY in place of some __REDIRECT. Reviewed-by: Siddhesh Poyarekar

C2x scanf binary constant handling

2023-03-02T19:10:37Z

C2x adds binary integer constants starting with 0b or 0B, and supports those constants for the %i scanf format (in addition to the %b format, which isn't yet implemented for scanf in glibc). Implement that scanf support for glibc. As with the strtol support, this is incompatible with previous C standard versions, in that such an input string starting with 0b or 0B was previously required to be parsed as 0 (with the rest of the input potentially matching subsequent parts of the scanf format string). Thus this patch adds 12 new __isoc23_* functions per long double format (12, 24 or 36 depending on how many long double formats the glibc configuration supports), with appropriate header redirection support (generally very closely following that for the __isoc99_* scanf functions - note that __GLIBC_USE (DEPRECATED_SCANF) takes precedence over __GLIBC_USE (C2X_STRTOL), so the case of GNU extensions to C89 continues to get old-style GNU %a and does not get this new feature). The function names would remain as __isoc23_* even if C2x ends up published in 2024 rather than 2023. When scanf %b support is added, I think it will be appropriate for all versions of scanf to follow C2x rules for inputs to the %b format (given that there are no compatibility concerns for a new format). Tested for x86_64 (full glibc testsuite). The first version was also tested for powerpc (32-bit) and powerpc64le (stdio-common/ and wcsmbs/ tests), and with build-many-glibcs.py.

Update copyright dates with scripts/update-copyrights

2023-01-06T21:14:39Z

Apply asm redirections in stdio.h before first use [BZ #27087]

2022-07-14T19:01:14Z

Compilers may not be able to apply asm redirections to functions after these functions are used for the first time, e.g. clang 13. Fix [BZ #27087] by applying all long double-related asm redirections before using functions in bits/stdio.h. However, as these asm redirections depend on the declarations provided by libio/bits/stdio2.h, this header was split in 2: - libio/bits/stdio2-decl.h contains all function declarations; - libio/bits/stdio2.h remains with the remaining contents, including redirections. This also adds the access attribute to __vsnprintf_chk that was missing. Tested with build-many-glibcs.py. Reviewed-by: Paul E. Murphy