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[Bug 1001635] New: wrong results from Cyg_StdioStream::read
- From: bugzilla-daemon at bugs dot ecos dot sourceware dot org
- To: unassigned at bugs dot ecos dot sourceware dot org
- Date: Fri, 27 Jul 2012 11:37:22 +0100
- Subject: [Bug 1001635] New: wrong results from Cyg_StdioStream::read
- Auto-submitted: auto-generated
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Summary: wrong results from Cyg_StdioStream::read
Product: eCos
Version: CVS
Platform: All
OS/Version: All
Status: UNCONFIRMED
Severity: normal
Priority: normal
Component: C library
AssignedTo: unassigned@bugs.ecos.sourceware.org
ReportedBy: bernd.edlinger@hotmail.de
CC: ecos-bugs@ecos.sourceware.org
Class: Advice Request
Created an attachment (id=1849)
--> (http://bugs.ecos.sourceware.org/attachment.cgi?id=1849)
proposed patch to fix this defect.
there are several different code paths which can lead to wrong results
in the function Cyg_StdioStream::read().
Please have a look at the following file:
"ecos/packages/language/c/libc/stdio/current/src/common/stream.cxx".
Suppose we are in unbuffered mode.
There may be an unread character in the "ungetc" buffer.
And there may be an unread character in the "readbuf_char" buffer.
Then the code may go thru the if statement in line 340, and
later thru the if statement in line 382.
BUG: in line 384: *bytes_read = 1; is wrong, we have 2 bytes read.
Now suppose we are in unbuffered mode again.
There may be an unread character in the "ungetc" buffer.
And the buffer_length may be 3 or higher.
Then the code may go thru the if statement in line 340, and
later thru the if statement in line 394.
BUG: user_buffer was already incremented in line 341. So the returned
data will contain an uninitialized byte in the middle.
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