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POWhat preprocessor directive or other method should I use to discern 32- vs 64-bit environment?
 

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  1. POWhat preprocessor directive or other method should I use to discern 32- vs 64-bit environment?
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    <p>I would like to compile the following <strong>C</strong> program for 32- and 64-bit systems.</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;stddef.h&gt; 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); } </code></pre> <p>What I have been doing with my <code>Makefile</code> is pass in <code>-m32</code> and <code>-64</code> to make bit-specific binaries:</p> <pre><code>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} ${ARRAY_64BIT_BINARY_NAME} ../bin </code></pre> <p>This works great, but I run into a warning when compiling:</p> <pre><code>$ 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 </code></pre> <p>What I would like to do is fix this warning without having two main.c files for two "bit" targets.</p> <p>Is there an <code>#ifndef</code> or other preprocessor conditional I can add to line 14 of <code>main.c</code> to handle this difference?</p> <p>Or is there a different and better way to handle this? </p> <p><strong>EDIT</strong>: I used the following solution:</p> <pre><code>#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 </code></pre>
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      1. POWhat preprocessor directive or other method should I use to discern 32- vs 64-bit environment?
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    1. COpossible duplicate of [How can I detect if I'm compiling for a 64bits architecture in C++](http://stackoverflow.com/questions/163058/how-can-i-detect-if-im-compiling-for-a-64bits-architecture-in-c)
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    2. CONot even close.
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