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D.gnu - Unused variables warning with -Wextra flag

reply "bdsatish" <bdsatish gmail.com> writes:
Hi,

Some warning messages are being "leaked" from GDC's source code 
into end-user's code. I think this shouldn't happen and hence, is 
a bug.

```
// example.d
import std.string;

void main()
{
   format("Hello World");
}

```
Here's the output:

```
[shell]$ gdc -Wextra example.d
$INSTALLDIR/gcc/include/d/4.8.0/std/utf.d: In function 'decode':
$INSTALLDIR/gcc/include/d/4.8.0/std/utf.d:856: warning: 
uninitialized variable 'result'
$INSTALLDIR/gcc/include/d/4.8.0/std/utf.d: In function 'decode':
$INSTALLDIR/gcc/include/d/4.8.0/std/utf.d:856: warning: 
uninitialized variable 'result'
$INSTALLDIR/gcc/include/d/4.8.0/std/utf.d: In function 'decode':
$INSTALLDIR/gcc/include/d/4.8.0/std/utf.d:856: warning: 
uninitialized variable 'result'
example.d: In function 
'std.format.formattedWrite!(Appender!(string), char, 
).formattedWrite':
$INSTALLDIR/gcc/include/d/4.8.0/std/format.d:504: warning: 
'iftmp.16' may be used uninitialized in this function
$INSTALLDIR/gcc/include/d/4.8.0/std/format.d:504: warning: 
'iftmp.17' may be used uninitialized in this function
```

So, all these warnings seem to be from GDC. Is there a way to 
supress these warnings? (for GDC's libs, not my own code).


--Satish
Feb 28 2013
next sibling parent Iain Buclaw <ibuclaw ubuntu.com> writes:
On Feb 28, 2013 6:55 PM, "bdsatish" <bdsatish gmail.com> wrote:

 Hi,

 Some warning messages are being "leaked" from GDC's source code into


end-user's code. I think this shouldn't happen and hence, is a bug.

 ```
 // example.d
 import std.string;

 void main()
 {
   format("Hello World");
 }

 ```
 Here's the output:

 ```
 [shell]$ gdc -Wextra example.d
 $INSTALLDIR/gcc/include/d/4.8.0/std/utf.d: In function 'decode':
 $INSTALLDIR/gcc/include/d/4.8.0/std/utf.d:856: warning: uninitialized


variable 'result'

 $INSTALLDIR/gcc/include/d/4.8.0/std/utf.d: In function 'decode':
 $INSTALLDIR/gcc/include/d/4.8.0/std/utf.d:856: warning: uninitialized


variable 'result'

 $INSTALLDIR/gcc/include/d/4.8.0/std/utf.d: In function 'decode':
 $INSTALLDIR/gcc/include/d/4.8.0/std/utf.d:856: warning: uninitialized


variable 'result'

 example.d: In function 'std.format.formattedWrite!(Appender!(string),


char, ).formattedWrite':

 $INSTALLDIR/gcc/include/d/4.8.0/std/format.d:504: warning: 'iftmp.16' may


be used uninitialized in this function

 $INSTALLDIR/gcc/include/d/4.8.0/std/format.d:504: warning: 'iftmp.17' may


be used uninitialized in this function

 ```

 So, all these warnings seem to be from GDC. Is there a way to supress


these warnings? (for GDC's libs, not my own code).

 --Satish


The iftmp's shouldn't be emitted, the others though are because it's a
template instantiated into the module you are compiling.

Regards
-- 
Iain Buclaw

*(p < e ? p++ : p) = (c & 0x0f) + '0';
Feb 28 2013
prev sibling parent reply Iain Buclaw <ibuclaw ubuntu.com> writes:
On 28 February 2013 21:45, Iain Buclaw <ibuclaw ubuntu.com> wrote:


 On Feb 28, 2013 6:55 PM, "bdsatish" <bdsatish gmail.com> wrote:

 Hi,

 Some warning messages are being "leaked" from GDC's source code into


 end-user's code. I think this shouldn't happen and hence, is a bug.

 ```
 // example.d
 import std.string;

 void main()
 {
   format("Hello World");
 }

 ```
 Here's the output:

 ```
 [shell]$ gdc -Wextra example.d
 $INSTALLDIR/gcc/include/d/4.8.0/std/utf.d: In function 'decode':
 $INSTALLDIR/gcc/include/d/4.8.0/std/utf.d:856: warning: uninitialized


 variable 'result'

 $INSTALLDIR/gcc/include/d/4.8.0/std/utf.d: In function 'decode':
 $INSTALLDIR/gcc/include/d/4.8.0/std/utf.d:856: warning: uninitialized


 variable 'result'

 $INSTALLDIR/gcc/include/d/4.8.0/std/utf.d: In function 'decode':
 $INSTALLDIR/gcc/include/d/4.8.0/std/utf.d:856: warning: uninitialized


 variable 'result'

 example.d: In function 'std.format.formattedWrite!(Appender!(string),


 char, ).formattedWrite':

 $INSTALLDIR/gcc/include/d/4.8.0/std/format.d:504: warning: 'iftmp.16'


 may be used uninitialized in this function

 $INSTALLDIR/gcc/include/d/4.8.0/std/format.d:504: warning: 'iftmp.17'


 may be used uninitialized in this function

 ```

 So, all these warnings seem to be from GDC. Is there a way to supress


 these warnings? (for GDC's libs, not my own code).

 --Satish


 The iftmp's shouldn't be emitted, the others though are because it's a
 template instantiated into the module you are compiling.

 Regards
 --
 Iain Buclaw

 *(p < e ? p++ : p) = (c & 0x0f) + '0';



Fixed both:
https://github.com/D-Programming-GDC/GDC/commit/064ca974963fd4a7e2d00254f448f529ecee7203

In the first instance, was because the code generation assumed that vresult
for a function get initialised on declaration.  For whatever reason this is
no longer the case (it gets constructed later).

In the second instance, the way gcc optimised the code paths for the
function, these values never got initialised.

In this instance, I see that this way being generated.

{
   uint iftmp;
   /* ... */
   {
      _d_array_bounds( ... );
      fun.2 = &fun.1 + iftmp;     // iftmp uninitialised here, however,
because of _d_array_bounds, we'll never hit this line in runtime.
      /* ... */
   }
}

The functions _d_array_bounds, and others in the family are strictly
speaking,  noreturn functions, as they do not return naturally apart from
through a thrown Exception / Error.   Have marked these library functions
as  noreturn so now the use of iftmp is optimised away.  So no false
positive warning will be emitted.


Regards
-- 
Iain Buclaw

*(p < e ? p++ : p) = (c & 0x0f) + '0';
Mar 01 2013
parent reply "bdsatish" <bdsatish gmail.com> writes:
Thanks Iain! Frankly, I'm new to GDC, so I didn't understand your 
explanation, but anyways, I'll pull from Git and re-check on my 
PC.

--Satish
Mar 01 2013
parent Iain Buclaw <ibuclaw ubuntu.com> writes:
On 1 March 2013 17:37, bdsatish <bdsatish gmail.com> wrote:


 Thanks Iain! Frankly, I'm new to GDC, so I didn't understand your
 explanation, but anyways, I'll pull from Git and re-check on my PC.

 --Satish


One was caused by a change in the front-end having a knock-on effect in
gdc.  The other caused by dead code elimination (and also the lack of in
this case).


Regards
-- 
Iain Buclaw

*(p < e ? p++ : p) = (c & 0x0f) + '0';
Mar 01 2013