From 5a9055ec26d9bb516bf01a33517609cb96778f56 Mon Sep 17 00:00:00 2001 From: solar Date: Tue, 14 Dec 2010 06:16:35 +0000 Subject: [PATCH] Fixed safeguard calculation in ftell(). git-svn-id: https://srv7.svn-repos.de/dev34/pdclib/trunk@493 546481bc-9713-0410-bf18-d3337bbf4a3e --- functions/stdio/ftell.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/functions/stdio/ftell.c b/functions/stdio/ftell.c index e392a8b..29c360a 100644 --- a/functions/stdio/ftell.c +++ b/functions/stdio/ftell.c @@ -28,12 +28,11 @@ long int ftell( struct _PDCLIB_file_t * stream ) i.e. unprocessed bytes as positive number. That is how the somewhat obscure return-value calculation works. */ - /* If offset is too large for return type, report error instead of wrong - offset value. Buffers may not be larger than INT_MAX so the casts are - safe. + /* If offset is too large for return type, report error instead of wrong + offset value. */ - /* FIXME: This calculation *underflows* when offset smaller than pre-read */ - if ( ( stream->pos.offset - ( (int)stream->bufend + (int)stream->ungetidx ) ) > ( LONG_MAX - stream->bufidx ) ) + /* TODO: Check what happens when ungetc() is called on a stream at offset 0 */ + if ( ( stream->pos.offset - stream->bufend ) > ( LONG_MAX - ( stream->bufidx - stream->ungetidx ) ) ) { /* integer overflow */ _PDCLIB_errno = _PDCLIB_ERANGE; -- 2.30.2