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Port recent MAX_RW_COUNT checks to POSIX

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* src/sysdep.c (MAX_RW_COUNT): Verify that it fits in POSIX standard
types, to go along with already-existing checks for MS-Windows types.
(emacs_intr_read): eassert on all platforms, not just MS-Windows.
This commit is contained in:
Paul Eggert 2018-02-20 13:42:20 -08:00
parent 630da78a3c
commit d599dce135
1 changed files with 19 additions and 10 deletions
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29
src/sysdep.c
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@ -2554,6 +2554,22 @@ emacs_close (int fd)
#define MAX_RW_COUNT (INT_MAX >> 18 << 18)
#endif
/* Verify that MAX_RW_COUNT fits in the relevant standard types. */
#ifndef SSIZE_MAX
# define SSIZE_MAX TYPE_MAXIMUM (ssize_t)
#endif
verify (MAX_RW_COUNT <= PTRDIFF_MAX);
verify (MAX_RW_COUNT <= SIZE_MAX);
verify (MAX_RW_COUNT <= SSIZE_MAX);
#ifdef WINDOWSNT
/* Verify that Emacs read requests cannot cause trouble, even in
64-bit builds. The last argument of 'read' is 'unsigned int', and
the return value's type (see 'sys_read') is 'int'. */
verify (MAX_RW_COUNT <= INT_MAX);
verify (MAX_RW_COUNT <= UINT_MAX);
#endif
/* Read from FD to a buffer BUF with size NBYTE.
If interrupted, process any quits and pending signals immediately
if INTERRUPTIBLE, and then retry the read unless quitting.
@ -2562,18 +2578,11 @@ emacs_close (int fd)
static ptrdiff_t
emacs_intr_read (int fd, void *buf, ptrdiff_t nbyte, bool interruptible)
{
/* No caller should ever pass a too-large size to emacs_read. */
eassert (nbyte <= MAX_RW_COUNT);
ssize_t result;
/* There is no need to check against MAX_RW_COUNT, since no caller ever
passes a size that large to emacs_read. */
#ifdef WINDOWSNT
/* On MS-Windows, 'read's last argument is declared as 'unsigned
int', and the return value's type (see 'sys_read') is 'int'.
This might cause trouble, especially in 64-bit builds, if the
above comment ever becomes incorrect. The following assertion
should make us more future-proof. */
eassert (nbyte <= INT_MAX);
#endif
do
{
if (interruptible)