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[Bug middle-end/16302] gcc fails to warn about some common logic errors
- From: "trt at acm dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 29 Apr 2005 20:20:13 -0000
- Subject: [Bug middle-end/16302] gcc fails to warn about some common logic errors
- References: <20040630193304.16302.trt@acm.org>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From trt at acm dot org 2005-04-29 20:20 -------
The patch given in comment #4 no successfully applies because the warning()
function has new initial parameter. Also the fold_buildN() cleanup invalidated
(and fixed) the "REAL_CST" part of the patch.
Some "speculative folding" is now causing false positives, for which there is a
simple fix: suppress warnings when doing such folds. For example
*** tree-ssa-loop-niter.c.orig Wed Apr 27 13:48:21 2005
--- tree-ssa-loop-niter.c Wed Apr 27 14:28:59 2005
***************
*** 778,780 ****
--- 778,782 ----
notcond = invert_truthvalue (cond);
+ inhibit_warnings++;
e = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, notcond, te);
+ inhibit_warnings--;
if (nonzero_p (e))
People who think warnings belong only in the front-end might balk. I could
submit an alternate indirect check for this situation in parser_build_binary_op.
It would be tidy, but would no longer warn about non-C glitches such as:
libjava/gnu/java/security/x509/X500DistinguishedName.java:447: if (sep !=
'+' || sep != ',')
libjava/java/net/HttpURLConnection.java:555: if (((code / 100) != 4) ||
((code / 100) != 5))
libjava/javax/swing/plaf/basic/BasicGraphicsUtils.java:401: if
((underlinedChar >= 0) || (underlinedChar <= 0xffff))
libjava/javax/security/auth/x500/X500Principal.java:380: if (sep != '+'
|| sep != ',')
Please let me know if there is any interest in a C-only patch. (Or any interest
in pursuing this PR.)
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16302