Fix issues in nickm's review of format_helper_exit_status for bug #1903

- Responsibility of clearing hex_errno is no longer with caller
- More conservative bounds checking
- Length requirement of hex_errno documented
- Output format documented
This commit is contained in:
Steven Murdoch 2010-10-04 14:14:11 +01:00
parent 80b515b85f
commit 5a77c64834
2 changed files with 35 additions and 14 deletions

View File

@ -2879,17 +2879,34 @@ load_windows_system_library(const TCHAR *library_name)
}
#endif
/** Format child_state and saved_errno as a hex string placed in hex_errno.
* Called between fork and _exit, so must be signal-handler safe */
/** Format <b>child_state</b> and <b>saved_errno</b> as a hex string placed in
* <b>hex_errno</b>. Called between fork and _exit, so must be signal-handler
* safe.
*
* <b>hex_errno</b> must have at least HEX_ERRNO_SIZE bytes available.
*
* The format of <b>hex_errno</b> is: "CHILD_STATE/ERRNO\n", left-padded
* with spaces. Note that there is no trailing \0. CHILD_STATE indicates where
* in the processs of starting the child process did the failure occur (see
* CHILD_STATE_* macros for definition), and SAVED_ERRNO is the value of
* errno when the failure occurred.
*/
void
format_helper_exit_status(unsigned char child_state, int saved_errno,
char *hex_errno)
{
/* Convert errno to be unsigned for hex conversion */
unsigned int unsigned_errno;
char *cur;
size_t i;
/* If errno is negative, negate it */
/* Fill hex_errno with spaces, and a trailing newline (memset may
not be signal handler safe, so we can't use it) */
for (i = 0; i < (HEX_ERRNO_SIZE - 1); i++)
hex_errno[i] = ' ';
hex_errno[HEX_ERRNO_SIZE - 1] = '\n';
/* Convert errno to be unsigned for hex conversion */
if (saved_errno < 0) {
unsigned_errno = (unsigned int) -saved_errno;
} else {
@ -2899,17 +2916,26 @@ format_helper_exit_status(unsigned char child_state, int saved_errno,
/* Convert errno to hex (start before \n) */
cur = hex_errno + HEX_ERRNO_SIZE - 2;
/* Check for overflow on first iteration of the loop */
if (cur < hex_errno)
return;
do {
*cur-- = "0123456789ABCDEF"[unsigned_errno % 16];
unsigned_errno /= 16;
} while (unsigned_errno != 0 && cur >= hex_errno);
/* Add on the minus side if errno was negative */
if (saved_errno < 0)
/* Prepend the minus sign if errno was negative */
if (saved_errno < 0 && cur >= hex_errno)
*cur-- = '-';
/* Leave a gap */
*cur-- = '/';
if (cur >= hex_errno)
*cur-- = '/';
/* Check for overflow on first iteration of the loop */
if (cur < hex_errno)
return;
/* Convert child_state to hex */
do {
@ -2970,10 +2996,6 @@ tor_spawn_background(const char *const filename, int *stdout_read,
and we are not allowed to use unsafe functions between fork and exec */
error_message_length = strlen(error_message);
/* Fill hex_errno with spaces, and a trailing newline */
memset(hex_errno, ' ', sizeof(hex_errno) - 1);
hex_errno[sizeof(hex_errno) - 1] = '\n';
child_state = CHILD_STATE_PIPE;
/* Set up pipe for redirecting stdout and stderr of child */

View File

@ -1212,14 +1212,13 @@ test_util_load_win_lib(void *ptr)
static void
clear_hex_errno(char *hex_errno)
{
memset(hex_errno, ' ', HEX_ERRNO_SIZE - 2);
hex_errno[HEX_ERRNO_SIZE - 1] = '\n';
hex_errno[HEX_ERRNO_SIZE] = '\0';
memset(hex_errno, '\0', HEX_ERRNO_SIZE + 1);
}
static void
test_util_exit_status(void *ptr)
{
/* Leave an extra byte for a \0 so we can do string comparison */
char hex_errno[HEX_ERRNO_SIZE + 1];
(void)ptr;