From: Xiang Gao Date: Fri, 8 May 2026 06:04:10 +0000 (+0800) Subject: libio: Ignore doallocate for open_memstream and open_wmemstream [BZ #34019] X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=97bd3b3d56ed867e7a545ce3501991a92df0d1bb;p=thirdparty%2Fglibc.git libio: Ignore doallocate for open_memstream and open_wmemstream [BZ #34019] setvbuf (stream, NULL, _IOFBF, 0) takes a special path in _IO_setvbuf: if the byte-oriented buffer base is NULL, it calls _IO_DOALLOCATE and returns without invoking the stream setbuf hook. For open_wmemstream, the byte-oriented buffer base is NULL although the wide result buffer has already been initialized in _wide_data. As a result, this path calls _IO_wdefault_doallocate, which may replace the wide buffer managed by open_wmemstream. Install an open_wmemstream-specific doallocate hook that leaves the growable result buffer unchanged. Add a regression test for this path. Install a narrow memstream doallocate hook as well. It keeps both memstream vtables consistent (generic stdio allocation must not replace the growable result buffer). Signed-off-by: Xiang Gao Reviewed-by: Adhemerval Zanella --- diff --git a/libio/Makefile b/libio/Makefile index 916542f23b..616107ee10 100644 --- a/libio/Makefile +++ b/libio/Makefile @@ -120,6 +120,7 @@ tests = \ tst-fwrite-error \ tst-getdelim \ tst-memstream-setbuf \ + tst-memstream-setvbuf-doallocate \ tst-memstream1 \ tst-memstream2 \ tst-memstream3 \ @@ -144,6 +145,7 @@ tests = \ tst-wfiledoallocate-static \ tst-widetext \ tst-wmemstream-setbuf \ + tst-wmemstream-setvbuf-doallocate \ tst-wmemstream1 \ tst-wmemstream2 \ tst-wmemstream3 \ diff --git a/libio/libioP.h b/libio/libioP.h index fd42307116..78e8ee6835 100644 --- a/libio/libioP.h +++ b/libio/libioP.h @@ -743,10 +743,12 @@ extern int _IO_mem_sync (FILE* fp) __THROW attribute_hidden; extern void _IO_mem_finish (FILE* fp, int) __THROW attribute_hidden; extern FILE *_IO_mem_setbuf (FILE *fp, char *buf, ssize_t size) __THROW attribute_hidden; +extern int _IO_mem_doallocate (FILE *fp) __THROW attribute_hidden; extern int _IO_wmem_sync (FILE* fp) __THROW attribute_hidden; extern void _IO_wmem_finish (FILE* fp, int) __THROW attribute_hidden; extern FILE *_IO_wmem_setbuf (FILE *fp, char *buf, ssize_t size) __THROW attribute_hidden; +extern int _IO_wmem_doallocate (FILE *fp) __THROW attribute_hidden; /* Other strfile functions */ struct _IO_strfile_; diff --git a/libio/memstream.c b/libio/memstream.c index 69b400d928..1af7224ab5 100644 --- a/libio/memstream.c +++ b/libio/memstream.c @@ -120,3 +120,12 @@ _IO_mem_setbuf (FILE *fp, char *p, ssize_t len) /* Memstream manage a growable buffer internally. */ return fp; } + + +int +_IO_mem_doallocate (FILE *fp) +{ + /* Memstream manage a growable buffer internally. The doallocate + hook must not replace it with a generic stdio buffer. */ + return 1; +} diff --git a/libio/tst-memstream-setvbuf-doallocate.c b/libio/tst-memstream-setvbuf-doallocate.c new file mode 100644 index 0000000000..aa6f86f02d --- /dev/null +++ b/libio/tst-memstream-setvbuf-doallocate.c @@ -0,0 +1,61 @@ +/* Test setvbuf on open_memstream, BZ #34019. + Copyright (C) 2026 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +#include + +static int +do_test (void) +{ + /* Regression test for setvbuf doallocate on open_memstream and + open_wmemstream. This test covers the _IO_setvbuf path for: + + setvbuf (stream, NULL, _IOFBF, 0) + + This path may call _IO_DOALLOCATE and return without invoking + the stream setbuf hook. The generic doallocate hook must not + replace the growable result buffer. */ + + CHAR_T *buf = NULL; + size_t len = 0; + FILE *fp = OPEN_MEMSTREAM (&buf, &len); + + TEST_VERIFY_EXIT (fp != NULL); + + TEST_COMPARE (setvbuf (fp, NULL, _IOFBF, 0), 0); + + TEST_COMPARE (FPUTC (W('A'), fp), W('A')); + TEST_COMPARE (fflush (fp), 0); + TEST_COMPARE (len, 1); + TEST_VERIFY_EXIT (buf != NULL); + TEST_VERIFY (buf[0] == W('A')); + TEST_VERIFY (buf[1] == W('\0')); + + TEST_COMPARE (FPUTC (W('B'), fp), W('B')); + TEST_COMPARE (fclose (fp), 0); + TEST_COMPARE (len, 2); + TEST_VERIFY_EXIT (buf != NULL); + TEST_VERIFY (buf[0] == W('A')); + TEST_VERIFY (buf[1] == W('B')); + TEST_VERIFY (buf[2] == W('\0')); + + free (buf); + + return 0; +} + +#include diff --git a/libio/tst-wmemstream-setvbuf-doallocate.c b/libio/tst-wmemstream-setvbuf-doallocate.c new file mode 100644 index 0000000000..857239aa85 --- /dev/null +++ b/libio/tst-wmemstream-setvbuf-doallocate.c @@ -0,0 +1,20 @@ +/* Test setvbuf on open_wmemstream, BZ #34019. + Copyright (C) 2026 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +#define TEST_WCHAR +#include diff --git a/libio/vtables.c b/libio/vtables.c index ca9f1b2dc4..ba3f9566f8 100644 --- a/libio/vtables.c +++ b/libio/vtables.c @@ -79,10 +79,12 @@ # pragma weak _IO_mem_finish # pragma weak _IO_mem_setbuf # pragma weak _IO_mem_sync +# pragma weak _IO_mem_doallocate # pragma weak _IO_wmem_finish # pragma weak _IO_wmem_setbuf # pragma weak _IO_wmem_sync +# pragma weak _IO_wmem_doallocate # pragma weak __printf_buffer_as_file_overflow # pragma weak __printf_buffer_as_file_xsputn @@ -338,7 +340,7 @@ const struct _IO_jump_t __io_vtables[] attribute_relro = JUMP_INIT (seekpos, _IO_default_seekpos), JUMP_INIT (setbuf, _IO_mem_setbuf), JUMP_INIT (sync, _IO_mem_sync), - JUMP_INIT (doallocate, _IO_default_doallocate), + JUMP_INIT (doallocate, _IO_mem_doallocate), JUMP_INIT (read, _IO_default_read), JUMP_INIT (write, _IO_default_write), JUMP_INIT (seek, _IO_default_seek), @@ -361,7 +363,7 @@ const struct _IO_jump_t __io_vtables[] attribute_relro = JUMP_INIT (seekpos, _IO_default_seekpos), JUMP_INIT (setbuf, _IO_wmem_setbuf), JUMP_INIT (sync, _IO_wmem_sync), - JUMP_INIT (doallocate, _IO_wdefault_doallocate), + JUMP_INIT (doallocate, _IO_wmem_doallocate), JUMP_INIT (read, _IO_default_read), JUMP_INIT (write, _IO_default_write), JUMP_INIT (seek, _IO_default_seek), diff --git a/libio/wmemstream.c b/libio/wmemstream.c index cdee2a4151..dffbb4a808 100644 --- a/libio/wmemstream.c +++ b/libio/wmemstream.c @@ -125,3 +125,12 @@ _IO_wmem_setbuf (FILE *fp, char *p, ssize_t len) /* Wmemstreams manage a growable buffer internally. */ return fp; } + + +int +_IO_wmem_doallocate (FILE *fp) +{ + /* Wmemstreams manage a growable buffer internally. The doallocate + hook must not replace it with a generic stdio buffer. */ + return 1; +}