Rich Felker
3af2edee15
when there is unflushed output, ftello (and ftell) compute the logical stream position as the underlying file descriptor's offset plus an adjustment for the amount of buffered data. however, this can give the wrong result for append-mode streams where the unflushed writes should adjust the logical position to be at the end of the file, as if a seek to end-of-file takes place before the write. the solution turns out to be a simple trick: when ftello (indirectly) calls lseek to determine the current file offset, use SEEK_END instead of SEEK_CUR if the stream is append-mode and there's unwritten buffered data. the ISO C rules regarding switching between reading and writing for a stream opened in an update mode, along with the POSIX rules regarding switching "active handles", conveniently leave undefined the hypothetical usage cases where this fix might lead to observably incorrect offsets. the bug being fixed was discovered via the test case for glibc issue
94 lines
2.3 KiB
C
94 lines
2.3 KiB
C
#ifndef _STDIO_IMPL_H
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#define _STDIO_IMPL_H
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#include <stdio.h>
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#include "syscall.h"
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#include "libc.h"
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#define UNGET 8
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#define FFINALLOCK(f) ((f)->lock>=0 ? __lockfile((f)) : 0)
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#define FLOCK(f) int __need_unlock = ((f)->lock>=0 ? __lockfile((f)) : 0)
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#define FUNLOCK(f) if (__need_unlock) __unlockfile((f)); else
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#define F_PERM 1
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#define F_NORD 4
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#define F_NOWR 8
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#define F_EOF 16
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#define F_ERR 32
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#define F_SVB 64
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#define F_APP 128
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struct _IO_FILE {
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unsigned flags;
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unsigned char *rpos, *rend;
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int (*close)(FILE *);
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unsigned char *wend, *wpos;
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unsigned char *mustbezero_1;
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unsigned char *wbase;
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size_t (*read)(FILE *, unsigned char *, size_t);
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size_t (*write)(FILE *, const unsigned char *, size_t);
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off_t (*seek)(FILE *, off_t, int);
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unsigned char *buf;
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size_t buf_size;
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FILE *prev, *next;
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int fd;
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int pipe_pid;
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long lockcount;
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short dummy3;
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signed char mode;
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signed char lbf;
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int lock;
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int waiters;
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void *cookie;
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off_t off;
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char *getln_buf;
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void *mustbezero_2;
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unsigned char *shend;
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off_t shlim, shcnt;
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};
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size_t __stdio_read(FILE *, unsigned char *, size_t);
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size_t __stdio_write(FILE *, const unsigned char *, size_t);
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size_t __stdout_write(FILE *, const unsigned char *, size_t);
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off_t __stdio_seek(FILE *, off_t, int);
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int __stdio_close(FILE *);
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size_t __string_read(FILE *, unsigned char *, size_t);
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int __toread(FILE *);
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int __towrite(FILE *);
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#if defined(__PIC__) && (100*__GNUC__+__GNUC_MINOR__ >= 303)
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__attribute__((visibility("protected")))
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#endif
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int __overflow(FILE *, int), __uflow(FILE *);
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int __fseeko(FILE *, off_t, int);
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int __fseeko_unlocked(FILE *, off_t, int);
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off_t __ftello(FILE *);
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off_t __ftello_unlocked(FILE *);
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size_t __fwritex(const unsigned char *, size_t, FILE *);
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int __putc_unlocked(int, FILE *);
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FILE *__fdopen(int, const char *);
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int __fmodeflags(const char *);
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#define OFLLOCK() LOCK(libc.ofl_lock)
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#define OFLUNLOCK() UNLOCK(libc.ofl_lock)
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#define feof(f) ((f)->flags & F_EOF)
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#define ferror(f) ((f)->flags & F_ERR)
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#define getc_unlocked(f) \
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( ((f)->rpos < (f)->rend) ? *(f)->rpos++ : __uflow((f)) )
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#define putc_unlocked(c, f) ( ((c)!=(f)->lbf && (f)->wpos<(f)->wend) \
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? *(f)->wpos++ = (c) : __overflow((f),(c)) )
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/* Caller-allocated FILE * operations */
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FILE *__fopen_rb_ca(const char *, FILE *, unsigned char *, size_t);
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int __fclose_ca(FILE *);
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#endif
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