[cfe-dev] switch over constant results in strange constructor/destructor ordering

Fletcher, John P via cfe-dev cfe-dev at lists.llvm.org
Sat Sep 17 08:29:17 PDT 2016


Richard

I see the same faulty output with Clang 3.6.0 and 3.8.0.

Is there anything which should be done about this pending an updated release?

Thanks

John

________________________________
From: cfe-dev [cfe-dev-bounces at lists.llvm.org] on behalf of Richard Smith via cfe-dev [cfe-dev at lists.llvm.org]
Sent: 17 September 2016 00:39
To: Andrew Johnson
Cc: Clang Dev
Subject: Re: [cfe-dev] switch over constant results in strange constructor/destructor ordering

Thanks for letting us know, fixed in r281797.

On Fri, Sep 16, 2016 at 2:13 PM, Richard Smith <richard at metafoo.co.uk<mailto:richard at metafoo.co.uk>> wrote:
Wow, yes, that's a (pretty scary) wrong-code bug. Working on it...

On Fri, Sep 16, 2016 at 6:47 AM, Andrew Johnson via cfe-dev <cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>> wrote:
Hello,

I'm seeing an unexpected construction/destruction order in the program below with clang 3.9.0. Is this considered a bug? Thank you.

clang asm - https://godbolt.org/g/uGlpFa
gcc asm - https://godbolt.org/g/WDgcZP

printf Output from clang (Unexpected):
obj entered 0
obj entered 1
obj entered 2
obj exited 2
obj exited 1
obj exited 0

printf Output from gcc (Expected):
obj entered 0
obj exited 0
obj entered 1
obj exited 1
obj entered 2
obj exited 2


Program:

#include <stdint.h>
#include <stdio.h>

class SomeClass
{
uint32_t k;
public:
SomeClass(uint32_t x)
        { k = x; printf("obj entered %d\n", k); }
~SomeClass()
        { printf("obj exited %d\n", k); }

};

int main()
{
uint32_t ii = 0;

switch(1)
{
default:
{

{
SomeClass someClass(ii++);
}

{
SomeClass someClass2(ii++);
}

{
SomeClass someClass3(ii++);
}
}
}
}


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