I would like to compile the following C program for 32- and 64-bit systems.
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
int main(int argc, char** argv) {
size_t size = atoi(argv[1]);
int *array;
array = malloc(size * sizeof(int));
if (array == NULL) {
fprintf(stderr, "could not allocate memory\n");
exit(1);
}
fprintf(stdout, "memory allocated on heap: %u bytes\n", sizeof(int)*size);
fprintf(stdout, "press Return to quit\n");
getchar();
fprintf(stdout, "freeing memory\n");
free(array);
exit(0);
}
What I have been doing with my Makefile is pass in -m32 and -64 to make bit-specific binaries:
CFLAGS=-ansi -pedantic -Wall -O3
32BIT_ARCH=-m32
64BIT_ARCH=-m64
32_CFLAGS=${32BIT_ARCH} ${CFLAGS}
64_CFLAGS=${64BIT_ARCH} ${CFLAGS}
CC=gcc
ARRAY_32BIT_BINARY_NAME=arrayTest32
ARRAY_64BIT_BINARY_NAME=arrayTest64
all: ${ARRAY_32BIT_BINARY_NAME} ${ARRAY_64BIT_BINARY_NAME}
arrayTest32: main32_array.o
${CC} ${32_CFLAGS} main32_array.o -o ${ARRAY_32BIT_BINARY_NAME}
arrayTest64: main64_array.o
${CC} ${64_CFLAGS} main64_array.o -o ${ARRAY_64BIT_BINARY_NAME}
main32_array.o: main.c
${CC} ${32_CFLAGS} -c main.c -o main32_array.o
main64_array.o: main.c
${CC} ${64_CFLAGS} -c main.c -o main64_array.o
clean:
-rm *.o *~ ${ARRAY_32BIT_BINARY_NAME} ${ARRAY_64BIT_BINARY_NAME}
install:
cp ${ARRAY_32BIT_BINARY_NAME} ${ARRAY_64BIT_BINARY_NAME} ../bin
This works great, but I run into a warning when compiling:
$ make
gcc -m32 -ansi -pedantic -Wall -O3 -c main.c -o main32_array.o
gcc -m32 -ansi -pedantic -Wall -O3 main32_array.o -o arrayTest32
gcc -m64 -ansi -pedantic -Wall -O3 -c main.c -o main64_array.o
main.c: In function ‘main’:
main.c:14: warning: format ‘%u’ expects type ‘unsigned int’, but argument 3 has type ‘long unsigned int’
gcc -m64 -ansi -pedantic -Wall -O3 main64_array.o -o arrayTest64
What I would like to do is fix this warning without having two main.c files for two “bit” targets.
Is there an #ifndef or other preprocessor conditional I can add to line 14 of main.c to handle this difference?
Or is there a different and better way to handle this?
EDIT: I used the following solution:
#if defined(__LP64__)
fprintf(stdout, "memory allocated on heap: %lu bytes\n", sizeof(int)*size);
#else
fprintf(stdout, "memory allocated on heap: %u bytes\n", sizeof(int)*size);
#endif
See here for a similar question.