Calling Conventions: Difference between revisions
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==Passing Function Arguments== |
==Passing Function Arguments== |
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GCC/x86 passes function arguments on the stack. These arguments are pushed in reverse order from their order in the argument list. Furthermore, since the x86 protected-mode stack operations operate on 32-bit values, the values are always pushed as a 32-bit value, even if the actual value is less than a full 32- |
GCC/x86 passes function arguments on the stack. These arguments are pushed in reverse order from their order in the argument list. Furthermore, since the x86 protected-mode stack operations operate on 32-bit values, the values are always pushed as a 32-bit value, even if the actual value is less than a full 32-bit value. Thus, for function <tt>foo()</tt>, the value of <tt>quux</tt> (a 48-bit FP value) is pushed first as two 32-bit values, low-32-bit-value first; the value of <tt>baz</tt> is pushed as the first byte of in 32-bit value; and then finally <tt>bar</tt> is pushed as a 32-bit value. |
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To pass arguments to a C function, the calling function must push the argument values as described above. Thus, to call foo() from a [[NASM]] assembly program, you would do something like this |
To pass arguments to a C function, the calling function must push the argument values as described above. Thus, to call foo() from a [[NASM]] assembly program, you would do something like this |
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