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POHow to use C defines in ARM assembler
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  1. POHow to use C defines in ARM assembler
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    copied!<p>How can I use external defines such as LONG_MIN and LONG_MAX in ARM assembler code?</p> <p>Let's say my_arm.h looks like this:</p> <pre><code>int my_arm(int foo); </code></pre> <p>Let's say I have a my_main.c as follows:</p> <pre><code>... #include &lt;limits.h&gt; #include "my_arm.h" ... int main (int argc, char *argv[]) { int foo=0; ... printf("My arm assembler function returns (%d)\n", my_arm(foo)); ... } </code></pre> <p>And my_arm.s looks like this:</p> <pre><code> .text .align 2 .global my_arm .type my_arm, %function my_arm: ... ADDS r1, r1, r2 BVS overflow ... overflow: LDR r0, LONG_MAX @ this is probably wrong, how to do it correctly? BX lr @ return with max value </code></pre> <p>The second to last line, I am not sure how to load correctly, I vaguely remember reading somewhere, that I had to define LONG_MAX in .global, but can't find the link to a working example anymore.</p> <p>I am compiling with arm-linux-gnueabi-gcc version 4.3.2</p> <p>==================</p> <p>UPDATE: Appreciate the suggestions! Unfortunately, I am still having trouble with syntax.</p> <p>First, I made a little header file mylimits.h (for now in same dir as .S)</p> <pre><code>#define MY_LONG_MIN 0x80000000 </code></pre> <p>in my_arm.S i added the following:</p> <pre><code>... .include "mylimits.h" ... ldr r7, =MY_LONG_MIN @ when it was working it was ldr r7, =0x80000000 ... </code></pre> <p>Two problems with this approach.</p> <p>First the biggest problem: the symbol MY_LONG_MIN is not recognized...so something is still not right</p> <p>Second: syntax for .include does not let me include <code>&lt;limits.h&gt;</code>, I would have to add that in mylimits.h, seems a bit kludgy, but I suppose, that is ok :)</p> <p>Any pointers?</p> <p>I have access to ARM System Developer’s Guide Designing and Optimizing System Software[2004] and ARM Architecture Reference Manual[2000], my target is XScale-IXP42x Family rev 2 (v5l) though.</p>
 

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