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Warning Cannot Optimize Possibly Infinite Loops

And then it finds a loop it's unable to optimize, and, exactly like you asked it to, it warns you that it found a loop it was unable to optimize. –jalf If it is talking about termination of the actual program generated by the compiler, then the C implementation is buggy because the data written into files (stdout is a file) differs Wmissing-noreturn Common Warning Alias(Wsuggest-attribute=noreturn) @@ -2500,8 +2500,8 @@ Perform loop unrolling for all loops. ; that control loops do not overflow and that the loops with nontrivial ; exit condition are Jones" To: libguestfs redhat com Subject: [Libguestfs] [PATCH 2/5] Avoid gcc warnings about infinite loop. http://bovbjerg.net/warning-cannot/warning-cannot.php

Possible repercussions from assault between coworkers outside the office Polyglot Anagrams Robbers' Thread Symmetric group action on Young Tableaux Is it possible to hand start modern planes? For now, I only added one specific interface number_of_iteration_exit_assumptions and this will only be used in vectorizer in my following patches. Comment 5 Jack Lloyd 2007-11-16 02:00:43 UTC Argh, you are correct. Bug?

share|improve this answer edited Jan 11 at 17:01 answered Feb 23 '15 at 18:44 Shafik Yaghmour 102k19236332 1 It seems that the C11 wording implies that while (1,1) /* no-op Find the "unwrapped size" of a list Using the eval command twice When does TNG take place in relation to DS9? N_("assuming that the loop is not infinite") - : N_("cannot optimize possibly infinite loops"); - warning (OPT_Wunsafe_loop_optimizations, "%s", - gettext (wording)); - } - if (desc->assumptions) - { - wording = Still I am surprised, I would have thought that compiler writers would purposely ignore the warnings raised by their own libraries because they had to employ those slight of hands just

Browse other questions tagged c optimization compiler-construction standards infinite-loop or ask your own question. If the > warning is highlighted potential issues that aren't due to the -f > option but are issues nonetheless, and we remove the warning, then how > should I go This option does nothing in this aspect. >>>>>> 2) IIRC, this option generates bogus code for some common programs, that's why it's disabled by default even at Ofast level. >>>>>> >>>>>> Does this apply to infinite goto loops as well?

And why no -O3? –Julio Gorgé Jan 29 '11 at 3:25 1 @Zorawar: and what if you copied here what's in /bits/stl_construct.h and identified the line 92 (note, only copying share|improve this answer answered Dec 8 '10 at 5:30 supercat 43.2k172110 You can belive even in God, but there is can be no ISO standard of the God behaviour. Currently the C11 standard does not contain the similar wording in section 5.1.2.4 Multi-threaded executions and data races but considering N1528 it seems wise to assume compilers will treat infinite goto IMHO, the old one reports weakness in loop niter analyzer, the issue exists whether I remove unsafe-loop-optimization or not.

I must admit I thought the compiler was always allowed to assume a loop would terminate eventually because deducing it would require solving the halting problem which cannot be solved in It also deletes the two now useless tests, while the option interface is preserved for backward compatibility purpose. It also deletes the two now useless tests, while the option interface is preserved for backward compatibility purpose. >>>> >>>> There are a number of bugs opened against those options, including By its name, this option does unsafe optimizations by assuming all loops must terminate and doesn't wrap.

Why does Cutie act like this and lesser robots listen to it? Hopefully WG14 will track any resulting changes. Unfortunately, it's not as useful as expected because: > 1) Simply assuming loop must terminate isn't enough. Generated at Fri Nov 11 04:12:08 CET 2016 using JIRA 7.1.7#71011-sha1:2526d7c13af2ab43673b0a163ceecff6fe735c9c. [package - head-mips-default][graphics/cairo] Failed for cairo-1.12.18_1, 2 in build pkg-fallout at FreeBSD.org pkg-fallout at FreeBSD.org Sun Jun 7 07:49:22 UTC

This leads to another problem about precise warning message: If a loop optimization has already handled loop with assumptions, we should not warn against the loop afterwards. navigate to this website This option does nothing in this aspect. >>> 2) IIRC, this option generates bogus code for some common programs, that's why it's disabled by default even at Ofast level. >>> >>> This was likely caused by different translation units being compiled with different visibility settings. and then intent as expressed in N1528 is that the C and C++ standard agree: Since compiler back-ends are typically shared between C and C++ compilers, it appears most important that

Not the answer you're looking for? gcc/testsuite/ChangeLog 2016-07-14 Bin Cheng * gcc.dg/tree-ssa/pr19210-1.c: Delete. * gcc.dg/tree-ssa/pr19210-2.c: Delete. Scanning dependencies of target LLVM [ 0%] Creating directories for 'LLVM' [ 0%] No download step for 'LLVM' [ 0%] No patch step for 'LLVM' [ 0%] No update step for More about the author Hi, Thanks for pointing me to these PRs, I will have a look at them.

The intent of these requirements is that unbuffered or line-buffered output appear as soon as possible, to ensure that prompting messages actually appear prior to a program waiting for input. does anything change if you remove it? –Marlon Jan 29 '11 at 3:17 Well, I guess it might keep the pedants away! (unless I'm mistaken, which I may very Target: x86_64-unknown-linux-gnu Configured with: ../gcc-4.2.0/configure --enable-languages=c,c++,objc,obj-c++ --program-suffix=-4.2.0 Thread model: posix gcc version 4.2.0 Comment 4 Andrew Pinski 2007-11-16 01:52:19 UTC (In reply to comment #3) > Here's another example, which I

Thanks, bin NightStrike July 18, 2016, 3:28 p.m.

This was likely caused by different translation units being compiled with different visibility settings. N_("assuming that the loop counter does not overflow") - : N_("cannot optimize loop, the loop counter may overflow"); - warning (OPT_Wunsafe_loop_optimizations, "%s", - gettext (wording)); - } - } - - What we really want is to analyze scalar evolution and loop niter bound under such assumptions. Isn't good old --funroll-loops good enough for you?

What we really want is to analyze scalar evolution and loop niter bound under such assumptions. This enables a wider range of loop optimizations even if the loop optimizer itself cannot prove that these assumptions are valid. Infinite loop?5Can an ANSI C compiler remove a delay loop?0Can compilers detect infinite looping condition?0An infinite loop3Compiler optimization for loops Hot Network Questions Can a president win the electoral college and click site Unfortunately, it's not as useful as expected because: >>>>>> 1) Simply assuming loop must terminate isn't enough.

What we really want is to analyze scalar evolution and loop niter bound under such assumptions. It also deletes the two now useless tests, while the option interface is preserved for backward compatibility purpose. >>> >>> There are a number of bugs opened against those options, including The warning you used should actually is usually coupled with -funsafe-loop-optimizations, from gcc optimize options page: -funsafe-loop-optimizations If given, the loop optimizer will assume that loop indices do not overflow, and Bug34114 - Missed optimization: cannot determine loop termination Summary: Missed optimization: cannot determine loop termination Status: RESOLVED FIXED Alias: None Product: gcc Classification: Unclassified Component: tree-optimization (show other bugs) Version: 4.3.0

ld: warning: direct access in __ZN5clang14FrontendAction15BeginSourceFileERNS_16CompilerInstanceERKNS_17FrontendInputFileE to global weak symbol __ZNK4llvm18IntrusiveRefCntPtrIN5clang10ASTContextEE6getPtrEv means the weak symbol cannot be overridden at runtime. Thanks, bin > > Richard. > >> Thanks, >> bin Patch hide | download patch | download mbox diff --git a/gcc/common.opt b/gcc/common.opt index a7c5125..331e1da 100644 --- a/gcc/common.opt +++ b/gcc/common.opt @@ -625,8 If the >>> warning is highlighted potential issues that aren't due to the -f >>> option but are issues nonetheless, and we remove the warning, then how >>> should I go How to handle a common misconception when writing a Master's thesis?

Yes, -fopt-info and -fopt-info-OPTIONS switches. On Sat, Jul 16, 2016 at 6:28 PM, NightStrike wrote: > On Fri, Jul 15, 2016 at 1:07 PM, Bin Cheng wrote: >> Hi, >> This patch removes support Hot Network Questions Safety - Improve braking power in wet conditions Problem with function inside brackets. Do we know Ford's old name?