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digitalmars.D.learn - dmd -O causes incorrect output

reply Saurabh Das <saurabh.das gmail.com> writes:
I'm seeing what appears to be a bug with the -O flag in dmd. Here 
is a reduced test case:

struct SomeStruct
{
     long value;
}
bool isNumberOne(int i)
{
	SomeStruct l;
	if(i == 1)
		l = SomeStruct(10);
	return (l == SomeStruct(10));
}
void main()
{
     if (!isNumberOne(1))
         assert(false);
}

See: https://run.dlang.io/is/zlrDvy




The assert trips when run with "rdmd -O test.d" and it does not 
trip when run with "rdmd test.d".

This bug is observed in all compiler versions from dmd-2.060 
through to dmd-2.095! Please shed some light on the issue – any 
help would be greatly appreciated.

Thanks,
Saurabh
Jan 25 2021
parent reply "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
On Mon, Jan 25, 2021 at 06:07:46PM +0000, Saurabh Das via Digitalmars-d-learn
wrote:

 I'm seeing what appears to be a bug with the -O flag in dmd.


[...]

 The assert trips when run with "rdmd -O test.d" and it does not trip
 when run with "rdmd test.d".


It's probably a bug. File a bug on bugzilla: https://issues.dlang.org



 This bug is observed in all compiler versions from dmd-2.060 through
 to dmd-2.095! Please shed some light on the issue – any help would be
 greatly appreciated.


[...]

DMD's backend is known to have obscure bugs that crop up every so often.
If this issue is being a showstopper, consider switching to LDC or GDC
instead.  (You might want to try the same code with LDC/GDC anyway, just
to see whether they have the same problem. My guess is they don't.)


T

-- 
People demand freedom of speech to make up for the freedom of thought which
they avoid. -- Soren Aabye Kierkegaard (1813-1855)
Jan 25 2021
parent reply Saurabh Das <saurabh.das gmail.com> writes:
On Monday, 25 January 2021 at 18:19:24 UTC, H. S. Teoh wrote:

 On Mon, Jan 25, 2021 at 06:07:46PM +0000, Saurabh Das via 
 Digitalmars-d-learn wrote:

 [...]


 [...]

 [...]


 It's probably a bug. File a bug on bugzilla: 
 https://issues.dlang.org



 [...]


 [...]

 DMD's backend is known to have obscure bugs that crop up every 
 so often. If this issue is being a showstopper, consider 
 switching to LDC or GDC instead.  (You might want to try the 
 same code with LDC/GDC anyway, just to see whether they have 
 the same problem. My guess is they don't.)


 T


LDMD2 seems to not suffer from this issue.
Jan 25 2021
parent reply "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
On Mon, Jan 25, 2021 at 06:45:43PM +0000, Saurabh Das via Digitalmars-d-learn
wrote:

 On Monday, 25 January 2021 at 18:19:24 UTC, H. S. Teoh wrote:


[...]

 It's probably a bug. File a bug on bugzilla: https://issues.dlang.org




[...]

 DMD's backend is known to have obscure bugs that crop up every so
 often.  If this issue is being a showstopper, consider switching to
 LDC or GDC instead.  (You might want to try the same code with
 LDC/GDC anyway, just to see whether they have the same problem. My
 guess is they don't.)




[...]

 LDMD2 seems to not suffer from this issue.


No surprise there. I recommend using LDC (ldmd2) instead.

Still file the bug, though, so that somebody will fix it eventually.


T

-- 
There is no gravity. The earth sucks.
Jan 25 2021
parent Saurabh Das <saurabh.das gmail.com> writes:
On Monday, 25 January 2021 at 19:18:47 UTC, H. S. Teoh wrote:

 On Mon, Jan 25, 2021 at 06:45:43PM +0000, Saurabh Das via 
 Digitalmars-d-learn wrote:

 On Monday, 25 January 2021 at 18:19:24 UTC, H. S. Teoh wrote:


 [...]

 It's probably a bug. File a bug on bugzilla: 
 https://issues.dlang.org




 [...]

 DMD's backend is known to have obscure bugs that crop up 
 every so often.  If this issue is being a showstopper, 
 consider switching to LDC or GDC instead.  (You might want 
 to try the same code with LDC/GDC anyway, just to see 
 whether they have the same problem. My guess is they don't.)




 [...]

 LDMD2 seems to not suffer from this issue.


 No surprise there. I recommend using LDC (ldmd2) instead.

 Still file the bug, though, so that somebody will fix it 
 eventually.


 T


Thanks for the inputs. I'll fill a bug report about it.
Jan 25 2021