Did I just find a bug in gcc/g++?

[Fusengammu]

Hello, I'm doing some calculations for my master's thesis, and I think I found a bug in gcc/g++. So can some knowledgeable person tell me whether it is/isn't a bug, and if so, should I report it to Apple?

So I boiled the problem down to 2 simple programs, one buggy and the other not:



fileTestB <filename> <param which causes bug>
and
fileTestNB <filename> <param which doesn't causes bug>





The program just tells you whether filename exists or not. fileTestB (the buggy one) tells me that a non-existent file exists if I give the third argument, while fileTestNB (Not buggy) tells me that a non-existent file doesn't exist whether I give the third param or not.




The buggy output looks like: (a file called "foo" doesn't exist)


****** ~ $ fileTestB foo argv3
****** PRINTING foo CAUSES BUG
****** foo is a regular file
****** ~ $ fileTestB foo
****** foo is a NOT a regular file


while the non-buggy output looks like


****** ~ $ fileTestNB foo argv3
****** PRINTING foo CAUSES NO BUG
****** foo is a NOT a regular file
****** ~ $ fileTestNB foo
****** foo is a NOT a regular file




The source code for the buggy and non-buggy programs are:



/******** begin code for "fileTestB" ********/
#include <cstdio>
#include <cstdlib>
#include <sys/stat.h>

int fexists(char *);

int main(int argc, char** argv)
{
if( argc < 2 )
{
fprintf(stderr, "fileTests <file or dir name> <3rd arg causes BUG>¥n");
exit(1);
}

if( argc == 3 )
{
// giving a 3rd argument causes BUG
printf(" PRINTING %s CAUSES BUG¥n", argv[1]);
}

if( fexists(argv[1]) )
{
printf("%s is a regular file¥n", argv[1]);
}
else
{
printf("%s is a NOT a regular file¥n", argv[1]);
}
}


int fexists(char *fname)
{
struct stat buffer;
stat(fname, &buffer);
return S_ISREG(buffer.st_mode);
}
/******** end code for "fileTestB" ********/






/******** begin code for "fileTestNB" ********/
#include <cstdio>
#include <cstdlib>
#include <sys/stat.h>

int main(int argc, char** argv)
{
if( argc < 2 )
{
fprintf(stderr, "fileTests <file or dir name> <3rd arg causes NO BUG>¥n");
exit(1);
}

if( argc == 3 )
{
// giving a 3rd argument causes NO BUG
printf(" PRINTING %s CAUSES NO BUG¥n", argv[1]);
}

struct stat buffer;
stat(argv[1], &buffer);

if( S_ISREG(buffer.st_mode) )
{
printf("%s is a regular file¥n", argv[1]);
}
else
{
printf("%s is a NOT a regular file¥n", argv[1]);
}
}
/******** end code for "fileTestB" ********/



I'm using OS X 10.3.9 on a Dual 2.5GHz G5.


thanx

 

[ElDiabloConCaca]

They worked just fine for me (meaning both programs correctly identified whether a file was a regular file or not, both with and without the 3rd argument), with a small change:

#include <cstdio>
#include <cstdlib>

to:

#include <stdio.h>
#include <stdlib.h>

The problem, I think, is that S_ISREG is a macro, so the scope of it needs to be clear. It seems that you cannot use a local macro in certain situations, as it will always return nil or something to that effect, but I can't remember the specifics of it. Also, S_ISREG() is not always defined on all systems, but that wouldn't explain why one correctly runs and the other doesn't.

Using gcc 4.0.1 on Tiger 10.4.3, G4 500MHz.

 

[Fusengammu]

yeah, i forgot to mention, i am using g++, hence the

#include <cstdio>


the thing that i don't understand is that on my linux machine, the code above works correctly, so it gives a different result than on my mac. and i thought as long as you were able to see a macro (meaning if it compiles), you could use it? are there more rules that have to be followed? because it seems like the macros work, but calling them from inside a function, they stop working (is this the scoping you were talking about?) all very confusing.

thankx though

 

[ElDiabloConCaca]

Hmmm... strange. I compiled your source again as-is with g++, and both programs work correctly on my machine.

Did you install g++ yourself, or have you installed the Apple Developer Tools/XCode?

I'm using g++ 4.0.1.

 

[Fusengammu]

Yeah, I installed Xcode (1.2) that came with my Panther install CD. Do you know if you have to be an ADC member to install Xcode updates?

thanx mr. concaca!

 

[Viro]

You have to be an ADC member, but the cost of registration is free. That should allow you to download XCode 1.5 for Panther.

 

[Fusengammu]

thanks, will get adc membership!