Issue 0429: Should gets_s discard next input line when (s == NULL) ?

This issue has been automatically converted from the original issue lists and some formatting may not have been preserved.

Authors: WG 14, Douglas Walls
Date: 2013-02-11
Reference document: N1673 N1748
Submitted against: C11 / C17
Status: Fixed
Fixed in: C17
Converted from: n2396.htm

Summary

gets_s Annex K.3.5.4.1p2 says:

"If there is a runtime-constraint violation, s[0] is set to the null
character, and characters are read and discarded from stdin until a
new-line character is read, or end-of-file or a read error occurs."

The runtime-constraint violation here can be caused by a null "s"
pointer.  Should we discard the next input line even if (s == NULL) ?

The way it is written, it looks like the answer is yes.  However it is
not clear to us that that was the intent.  Note also that s[0] cannot be
set to the null character when s==NULL.

Suggested Technical Corrigendum

Comment from WG14 on 2017-11-03:

Apr 2013 meeting

Committee Discussion

• The issue is found in Annex K.3.5.4.1p3, not p2.
• The Microsoft implementation appears to treat this as a runtime-constraint violation.
• The Dikumware implementation leaves this behavior unspecified.

Oct 2013 meeting

Committee Discussion

• Given that footnote 404 already provides guidance on this issue, the author and the committee agree that the answer to the question posed is indeed yes.
• The other issue with respect to s[0] cannot be set to the null character when s==NULL has been determined to be resolved by the following changes.

Proposed Technical Corrigendum

In Annex K.3.5.4.1, replace paragraph 3 with the following:

If there is a runtime-constraint violation, characters are read and discarded from stdin until a new-line character is read, or end-of-file or a read error occurs, and if s is not a null pointer s[0] is set to the null character.