diff options
Diffstat (limited to 'src/common/psprintf.c')
| -rw-r--r-- | src/common/psprintf.c | 73 |
1 files changed, 14 insertions, 59 deletions
diff --git a/src/common/psprintf.c b/src/common/psprintf.c index b974a99be12..04465a18e69 100644 --- a/src/common/psprintf.c +++ b/src/common/psprintf.c @@ -77,7 +77,7 @@ psprintf(const char *fmt,...) * pvsnprintf * * Attempt to format text data under the control of fmt (an sprintf-style - * format string) and insert it into buf (which has length len, len > 0). + * format string) and insert it into buf (which has length len). * * If successful, return the number of bytes emitted, not counting the * trailing zero byte. This will always be strictly less than len. @@ -89,14 +89,11 @@ psprintf(const char *fmt,...) * Other error cases do not return, but exit via elog(ERROR) or exit(). * Hence, this shouldn't be used inside libpq. * - * This function exists mainly to centralize our workarounds for - * non-C99-compliant vsnprintf implementations. Generally, any call that - * pays any attention to the return value should go through here rather - * than calling snprintf or vsnprintf directly. - * * Note that the semantics of the return value are not exactly C99's. * First, we don't promise that the estimated buffer size is exactly right; * callers must be prepared to loop multiple times to get the right size. + * (Given a C99-compliant vsnprintf, that won't happen, but it is rumored + * that some implementations don't always return the same value ...) * Second, we return the recommended buffer size, not one less than that; * this lets overflow concerns be handled here rather than in the callers. */ @@ -105,28 +102,10 @@ pvsnprintf(char *buf, size_t len, const char *fmt, va_list args) { int nprinted; - Assert(len > 0); - - errno = 0; - - /* - * Assert check here is to catch buggy vsnprintf that overruns the - * specified buffer length. Solaris 7 in 64-bit mode is an example of a - * platform with such a bug. - */ -#ifdef USE_ASSERT_CHECKING - buf[len - 1] = '\0'; -#endif - nprinted = vsnprintf(buf, len, fmt, args); - Assert(buf[len - 1] == '\0'); - - /* - * If vsnprintf reports an error other than ENOMEM, fail. The possible - * causes of this are not user-facing errors, so elog should be enough. - */ - if (nprinted < 0 && errno != 0 && errno != ENOMEM) + /* We assume failure means the fmt is bogus, hence hard failure is OK */ + if (unlikely(nprinted < 0)) { #ifndef FRONTEND elog(ERROR, "vsnprintf failed: %m"); @@ -136,42 +115,21 @@ pvsnprintf(char *buf, size_t len, const char *fmt, va_list args) #endif } - /* - * Note: some versions of vsnprintf return the number of chars actually - * stored, not the total space needed as C99 specifies. And at least one - * returns -1 on failure. Be conservative about believing whether the - * print worked. - */ - if (nprinted >= 0 && (size_t) nprinted < len - 1) + if ((size_t) nprinted < len) { /* Success. Note nprinted does not include trailing null. */ return (size_t) nprinted; } - if (nprinted >= 0 && (size_t) nprinted > len) - { - /* - * This appears to be a C99-compliant vsnprintf, so believe its - * estimate of the required space. (If it's wrong, the logic will - * still work, but we may loop multiple times.) Note that the space - * needed should be only nprinted+1 bytes, but we'd better allocate - * one more than that so that the test above will succeed next time. - * - * In the corner case where the required space just barely overflows, - * fall through so that we'll error out below (possibly after - * looping). - */ - if ((size_t) nprinted <= MaxAllocSize - 2) - return nprinted + 2; - } - /* - * Buffer overrun, and we don't know how much space is needed. Estimate - * twice the previous buffer size, but not more than MaxAllocSize; if we - * are already at MaxAllocSize, choke. Note we use this palloc-oriented - * overflow limit even when in frontend. + * We assume a C99-compliant vsnprintf, so believe its estimate of the + * required space, and add one for the trailing null. (If it's wrong, the + * logic will still work, but we may loop multiple times.) + * + * Choke if the required space would exceed MaxAllocSize. Note we use + * this palloc-oriented overflow limit even when in frontend. */ - if (len >= MaxAllocSize) + if (unlikely((size_t) nprinted > MaxAllocSize - 1)) { #ifndef FRONTEND ereport(ERROR, @@ -183,8 +141,5 @@ pvsnprintf(char *buf, size_t len, const char *fmt, va_list args) #endif } - if (len >= MaxAllocSize / 2) - return MaxAllocSize; - - return len * 2; + return nprinted + 1; } |