conversion warning

[Alexandru Mosoi]

Hi

Recently I've made a stupid bug. Here is a snippet:

long long a, b;
....
int c = min(a, b);

But this bug could have been prevented if g++ would warn me about loss
of precision. Do you know any flag that can turn on this kind of
warning? I tried -Wconversion, but I believe it's working only on
float <-double conversion.

Alexandru

[Victor Bazarov]

Alexandru Mosoi wrote:

Recently I've made a stupid bug. Here is a snippet:

long long a, b;
...
int c = min(a, b);

Note that C++ does not have 'long long' type.

But this bug could have been prevented if g++ would warn me about loss
of precision. Do you know any flag that can turn on this kind of
warning? I tried -Wconversion, but I believe it's working only on
float <-double conversion.

If you need an answer to a G++ specific question, consider posting
to the G++ specific newsgroup, please.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[BobR]

Alexandru Mosoi wrote in message...

Hi
Recently I've made a stupid bug. Here is a snippet:

long long a, b;
...
int c = min(a, b);

But this bug could have been prevented if g++ would warn me about loss
of precision. Do you know any flag that can turn on this kind of
warning? I tried -Wconversion, but I believe it's working only on
float <-double conversion.
Alexandru

Why not just check it:

{
long long a, b;

...

if( min(a, b) long long( std::numeric_li mits<int>::max( ) ) ){
throw std::runtime_er ror(" result too large for type int.");
}
int c = min(a, b);
}

Or, truncate it:

int c = ( min(a, b) & 0x7fffffff ); // assuming sizeof int == 4

Check if it was truncated:

if( long long( c ) != min(a, b) ){
std::cout<<"Tru ncated"<<'\n';
}

For compiler questions, you need to ask on an NG for your compiler.
For GCC g++, gnu.g++.help
I think if you just turn on warnings (-Wall -W), it will tell you of
incorrect assignments. ( I've got a big project in progress, or I'd test
that out.)

Also:
-Wlong-long
Warn if long long type is used. This is default. To inhibit the warning
messages, use -Wno-long-long. Flags -Wlong-long and -Wno-long-long are taken
into account only when -pedantic flag is used.

--
Bob R
POVrookie

[Alexandru Mosoi]

On Sep 9, 12:08 am, "BobR" <removeBadB...@ worldnet.att.ne twrote:

Alexandru Mosoi wrote in message...

Hi
Recently I've made a stupid bug. Here is a snippet:

long long a, b;
...
int c = min(a, b);

But this bug could have been prevented if g++ would warn me about loss
of precision. Do you know any flag that can turn on this kind of
warning? I tried -Wconversion, but I believe it's working only on
float <-double conversion.
Alexandru

Why not just check it:

{
long long a, b;...

if( min(a, b) long long( std::numeric_li mits<int>::max( ) ) ){
throw std::runtime_er ror(" result too large for type int.");
}
int c = min(a, b);

}

Or, truncate it:

int c = ( min(a, b) & 0x7fffffff ); // assuming sizeof int == 4

Check if it was truncated:

if( long long( c ) != min(a, b) ){
std::cout<<"Tru ncated"<<'\n';
}

None of you solution is good for me because I accidentally wrote _int
c_ instead of _long long c_. However I would have avoided the mistake
if compiler was a little bit clever. I've done the bug in a
programming contest where you don't really care about portability and
stuff like that. If it compiles than it perfect. However little
warnings are more than welcome.

>
For compiler questions, you need to ask on an NG for your compiler.
For GCC g++, gnu.g++.help

hmm... i've posted a message, i'm waiting for a reply.

I think if you just turn on warnings (-Wall -W), it will tell you of
incorrect assignments. ( I've got a big project in progress, or I'd test
that out.)

Also:
-Wlong-long
Warn if long long type is used. This is default. To inhibit the warning
messages, use -Wno-long-long. Flags -Wlong-long and -Wno-long-long are taken
into account only when -pedantic flag is used.

>
--
Bob R
POVrookie