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    <blockquote> <p>what am I doing wrong?</p> </blockquote> <p><strong>First</strong>: make sure you are using the right calling convention (stack, registers, left to right, right to left, etc.). If your program indeed prints a floating point number, although it is not the one you required, then at least the format string is being passed correctly (or you are having a lot of luck and <code>printf</code> found the address of the format string at the right place even if you didn't put its address there).</p> <p><strong>Second</strong>: the number you are trying to print... is it a float or a double? <code>rs</code> is defined to hold a quadword value (64 bits), but floats are 32 bits. So, if the first point has been checked and it's ok, I suggest you to use <code>"%lf"</code> as format, instead of <code>"%f"</code>.</p> <p>BTW: why do you put <code>RAX = 0</code>? What does it mean regarding the call to <code>printf</code>?</p> <p>UPDATE: This may help you. A disassembly of a silly program (<code>f.c</code>):</p> <pre><code>#include &lt;stdio.h&gt; main() { float x; x = 1.6; printf ("%f\n", x); } </code></pre> <p><code>$ gcc -c -S f.c</code></p> <p><code>$ less f.s</code></p> <pre><code> .file "f.c" .section .rodata .LC1: .string "%f\n" .text .globl main .type main, @function main: .LFB0: .cfi_startproc pushq %rbp .cfi_def_cfa_offset 16 movq %rsp, %rbp .cfi_offset 6, -16 .cfi_def_cfa_register 6 subq $16, %rsp movl $0x3fcccccd, %eax movl %eax, -4(%rbp) movss -4(%rbp), %xmm0 cvtps2pd %xmm0, %xmm0 movl $.LC1, %eax movq %rax, %rdi movl $1, %eax call printf leave </code></pre>
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    1. POprintf float in nasm assembly 64-bit
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    1. COrax actually al should hold the number of xmm registers used, I changed it to one but now the program crashes with a seg fault in printf. the floating arguments of printf are stored in the xmm registers (amd64 assembler), the string address is stored in rdi.
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    2. CODid you tried changing the string format to `%lf` ?
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    3. COyes, but it still crashes
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