Problem with running program using GCC

[theRandy]

Ok so im trying to run the following code to show the different sizes of data types:

#include <stdio.h>

int main() {
printf("The 'int' data type is\t\t %d bytes\n", sizeof(int));
printf("The 'unsigned int' data type is\t %d bytes\n", sizeof(unsigned));
printf("The 'short int' data type is\t %d bytes\n", sizeof(short int));
printf("The 'long int' data type is\t %d bytes\n", sizeof(long int));
printf("The 'long long int' data type is\t %d bytes\n", sizeof(long long int));
printf("The 'float' data type is\t %d bytes\n", sizeof(float));
printf("The 'char' data type is\t\t %d bytes\n", sizeof(char));
}

when i try compile it with GCC i get the error message

root@bt:~/Documents/Programming# gcc datatype_sizes.c -fno-builtin -g
datatype_sizes.c: In function ‘main’:
datatype_sizes.c:10: error: expected declaration or statement at end of input
root@bt:~/Documents/Programming#


and when i use ls -l a.out and then try to run the program using ./a.out it runs the wrong piece of code:

root@bt:~/Documents/Programming# gcc datatype_sizes.c -fno-builtin -g
datatype_sizes.c: In function ‘main’:
datatype_sizes.c:10: error: expected declaration or statement at end of input
root@bt:~/Documents/Programming# ls -l a.out
-rwxr-xr-x 1 root root 8471 2013-06-21 14:37 a.out
root@bt:~/Documents/Programming# ./a.out
Hello, world!

Hello, world!

Hello, world!

Hello, world!

Hello, world!

Hello, world!

Hello, world!

Hello, world!

Hello, world!

Hello, world!



Any idea why this is happening, ive never had this problem up until now with GCC.

[sanderj]

No problems here ...

sander@flappie:~$ gcc blabla.c
sander@flappie:~$ ./a.out
The 'int' data type is 4 bytes
The 'unsigned int' data type is 4 bytes
The 'short int' data type is 2 bytes
The 'long int' data type is 8 bytes
The 'long long int' data type is 8 bytes
The 'float' data type is 4 bytes
The 'char' data type is 1 bytes
sander@flappie:~$

[pmu]

Hi,

Your a.out would be an executable of a previous code that you compiled.

Did you try compiling without the -fno-builtin -g ?

[sanderj]

No, it can't be.
And yes, I just compiled like I posted; with a plain "gcc". See here again:

sander@flappie:~$ gcc blabla.c -o blablabla
sander@flappie:~$ ./blablabla
The 'int' data type is 4 bytes
The 'unsigned int' data type is 4 bytes
The 'short int' data type is 2 bytes
The 'long int' data type is 8 bytes
The 'long long int' data type is 8 bytes
The 'float' data type is 4 bytes
The 'char' data type is 1 bytes
sander@flappie:~$

[theRandy]

Yes i tried it with fno-builtin. without it i get more error messages:


root@bt:~/Documents/Programming# gcc datatype_sizes.c
datatype_sizes.c: In function ‘main’:
datatype_sizes.c:4: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long unsigned int’
datatype_sizes.c:5: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long unsigned int’
datatype_sizes.c:6: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long unsigned int’
datatype_sizes.c:7: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long unsigned int’
datatype_sizes.c:8: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long unsigned int’
datatype_sizes.c:9: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long unsigned int’
datatype_sizes.c:10: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long unsigned int’
datatype_sizes.c:10: error: expected declaration or statement at end of input

[theRandy]

Ahhh never mind i screwed up and accidentally saved the same code twice one without a curly bracket at the end and one with on my desktop accidentally..... Working fine now:


root@bt:~/Documents/Programming# gcc -fno-builtin datatype_sizes.c
root@bt:~/Documents/Programming# ./a.out
The 'int' data type is 4 bytes
The 'unsigned int' data type is 4 bytes
The 'short int' data type is 2 bytes
The 'long int' data type is 8 bytes
The 'long long int' data type is 8 bytes
The 'float' data type is 4 bytes
The 'char' data type is 1 bytes


:redface: My bad

[dwhitney67]

I'm not sure why you felt compelled to use the -fno-builtin option for such a trivial program.

The -g option is used to ensure that symbolic information is included within the produced executable; again, IMHO, unnecessary for your program.

The warning you got earlier regarding the "format '%d' expects ..." is due to the fact that you are attempting to print the value returned by sizeof(), which is not an int, but instead a long unsigned int. You would be better off using '%lu' as your format statement in the printf() calls.

Lastly, why are you working as the root-user on your system?

[trent.josephsen]

sizeof gives a size_t, which happens to be an unsigned long for you, but you would do well to use the %zu specifier instead, which is defined by C99. You're relying on two C99 features already, as gcc will be happy to warn you if you compile with -pedantic, so use -std=c99 (or -std=c11) to make sure you don't run into any additional standard-related problems.

gcc by default compiles a bastardized version of C and enables no optional warnings. You will get much better diagnostics if you specify a language standard and ask for all the diagnostics. When I am compiling a lot from the command line, I alias cc to "gcc -std=c11 -pedantic -Wall -Wextra -Wwrite-strings" to save typing.