similar to: clang-tidy : Modify cert-err60-cpp configuration

> I think we can do such optimization with operator new, because new never returns null. This is incorrect in the case of `new (std::nothrow) ...` - the whole point of `(std::nothrow)` is to tell new that it should return NULL in case of failure, rather than throw an exception (bad_alloc). But the point here is not the actual return value, but the fact that the compiler misses that the

Hi Mats, I think Kevin's point is malloc can return 0, if malloc/free pair is optimized way, the semantic of the original would be changed. On the other hand, malloc/free are special functions, but programmers can still define their own versions by not linking std library, so we must assume malloc/free always have side-effect like other common functions, unless we know we will link std

Hi, When looking into the bug in https://llvm.org/bugs/show_bug.cgi?id=21421, I found a regression test in Transforms/InstCombine/malloc-free-delete.ll against me to directly fix it. The test is, define i1 @foo() { ; CHECK-LABEL: @foo( ; CHECK-NEXT: ret i1 false %m = call i8* @malloc(i32 1) %z = icmp eq i8* %m, null call void @free(i8* %m) ret i1 %z } According to

Hi David and Mats, Thanks for your explanation. If my understanding is correct, it means we don't need to consider the side-effect of malloc/free unless compiling with -ffreestanding. Because without -ffreestanding, user defined malloc/free should be compatible with std library. It makes sense to me. My point is, in std library, malloc is allowed to return null if this malloc failed. Why

I just installed the pre-compiled binaries for Clang 3.4.1, which was the latest version I could find to download. Starting a new 'blank' project in MSVC I was easily able to change the tool set from MS Visual Studio 2013 (v120) to LLVM-vs2013. However, trying to compile a simple 'hello world' program resulted in the following compiler errors. Is there something simple I am

Hi, Jonas! On Tue, Nov 1, 2016 at 3:26 AM, Jonas Wagner <jonas.wagner at epfl.ch> wrote: > Hi Eugene, > > I think this is really cool! You've convinced me to try out PVS on some of > my own projects :) > > Of all the warnings presented in the article, there was one for which I > thought it's a false positive. By default, LLVM is compiled without RTTI and >

On Wed, Nov 2, 2016 at 9:41 AM, Jonas Wagner via llvm-dev < llvm-dev at lists.llvm.org> wrote: > Hello, > > I think this should be added by Clang itself. > > > I don't think so. There are several sources online that indicate that > developers need to *manually* specify std::nothrow. If they don't, > operator new will throw an exception even if code is

Folks, I'm sorry for getting at this again, but this will not be the last discussion on the topic, so let's just get to business. We're about to merge the last critical patch to make EHABI compatible with other EH mechanisms in LLVM (D3079), and that has unearthed a few issues with the function attributes. Logan's blog post [1] contains a proposal to split unwinding from

Hi Michael, On Mon, Jan 2, 2017 at 11:49 PM, Michael Kuperstein <michael.kuperstein at gmail.com> wrote: > This sounds right to me. > > IIUC, historically, readonly and readnone are meant to model the "pure" and > "const" GCC attributes. These attributes make pretty strong guarantees: > > "[a pure] function can be subject to common subexpression

On Thu, Aug 13, 2020 at 6:35 PM Haoran Xu <haoranxu510 at gmail.com> wrote: > > Thanks for the reply. > >> Sorry, yes. No difference between explicit error handling and >> exceptions. The difference is in all the functions that don't have >> explicit error handling but (in the exception-using equivalent code) >> aren't marked nothrow (where, without

On Wed, Feb 25, 2015 at 10:35 AM, Ilia Mirkin <imirkin at alum.mit.edu> wrote: > pthread_mutex_lock had *better* imply a compiler barrier across which > code can't be moved... which is very different from the printf case > where it might have done it due to register pressure or who knows > what. > In the dummy function, register pressure was certainly not an issue, but

On Thu, Aug 13, 2020 at 6:11 PM Haoran Xu <haoranxu510 at gmail.com> wrote: > > Thanks for the insights David! > > For your first 3 points, is it correct to understand it as following: the external function prototypes are missing reliable information on whether the function throws and what exceptions it may throw (due to C++'s design failures and that it is impractical to

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Folks, We're having some discussions about the behaviour of exception handling and Dwarf sharing unwind logic, tables, etc. and it seems that the code around it wasn't designed with any particular goal in mind, but evolved (like the EHABI) and now we're seeing the results from it. The problems below are assuming C vs. C++, but it actually apply to any possibly-exceptional vs.

I recall it was things we could deduce by scanning the method before we optimized it, eg deduced noreturn/nothrow. I'd have to go check to be sure. Once you allow inlining, you're pretty much telling your users they had better give you compatible definitions. We wanted to make sure that if users gave us compatible defs (mainly: same source, but optimized in one CU and not in another),

On Tue, Apr 13, 2010 at 09:01:16AM +0200, Duncan Sands wrote: > Hi Jack, > >> bash-3.2$ gcc-4 hello.c -S -O1 -o - -fplugin=./dragonegg.so >> cc1: error: Cannot load plugin ./dragonegg.so >> dlopen(./dragonegg.so, 10): Symbol not found: _classify_argument > > looks like you forgot to apply the i386_static.diff patch to gcc. > > Ciao, > > Duncan. Duncan,

On Tue, Jan 3, 2017 at 10:47 AM, Michael Kuperstein via llvm-dev < llvm-dev at lists.llvm.org> wrote: > > > On Tue, Jan 3, 2017 at 9:59 AM, Sanjoy Das via llvm-dev < > llvm-dev at lists.llvm.org> wrote: > >> Hi Michael, >> >> On Mon, Jan 2, 2017 at 11:49 PM, Michael Kuperstein >> <michael.kuperstein at gmail.com> wrote: >> > This

> On Jul 21, 2016, at 7:45 AM, Philip Reames <listmail at philipreames.com> wrote: > > Joining in very late, but the tangent here has been interesting (if rather OT for the original thread). > > I agree with Danny that we might want to take a close look at how we model things like maythrow calls, no return, and other implicit control flow. I'm not convinced that moving

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On Thu, Aug 13, 2020 at 4:38 PM Haoran Xu <haoranxu510 at gmail.com> wrote: > > Hello David and Sterling, thanks for the reply! > > I have no intention to heat up the discussion, please pardon me if I asked questions that might sound silly to you -- it's just that I truly didn't understand since I'm not expert in llvm or optimizer or exception handling at all. >