On 29.11.2014 13:56, Ewald wrote:
On 11/29/2014 12:41 AM, Flávio Etrusco wrote:
Are you sure it's not the result that is passed in the first parameter?
http://en.wikipedia.org/wiki/X86_calling_conventions#cdecl
Good question, but I don't think so. The first few lines of assembly
from this function seem to read three arguments you see:
44b360: 53 push %rbx
44b361: 41 54 push %r12
44b363: 41 55 push %r13
44b365: 48 89 fb mov %rdi,%rbx <-- first
argument, %rdi
44b368: 41 89 f4 mov %esi,%r12d <-- second
argument, %rsi
44b36b: 49 89 d5 mov %rdx,%r13 <-- third
argument, %rdx
What I forgot to mention was that this is on a x86_64 architecture, so I
based myself on the table found at
http://wiki.osdev.org/Calling_Conventions .
Just compile with "-al" and you'll see what the compiler uses the
parameters for (the following example is for i386):
=== listing begin ===
.section .text
.balign 16,0x90
.globl P$TCALLCONV_SOMEFUNCTION$PCHAR$LONGWORD$$ANSISTRING
.type P$TCALLCONV_SOMEFUNCTION$PCHAR$LONGWORD$$ANSISTRING,@function
P$TCALLCONV_SOMEFUNCTION$PCHAR$LONGWORD$$ANSISTRING:
.Lc1:
# Temps allocated between ebp-524 and ebp-12
# [callconv.pp]
# [6] begin
pushl %ebp
.Lc3:
.Lc4:
movl %esp,%ebp
.Lc5:
subl $524,%esp
# Var aData located at ebp-4
# Var aLen located at ebp-8
# Var $result located at ebp-12
movl %eax,-4(%ebp)
movl %edx,-8(%ebp)
movl %ecx,-12(%ebp)
# [7] Result := Copy(StrPas(aData), 1, aLen);
leal -268(%ebp),%eax
pushl %eax
leal -524(%ebp),%edx
movl -4(%ebp),%eax
call SYSTEM_STRPAS$PCHAR$$SHORTSTRING
leal -524(%ebp),%eax
movl -8(%ebp),%ecx
movl $1,%edx
call fpc_shortstr_copy
leal -268(%ebp),%eax
movl -12(%ebp),%edx
call fpc_shortstr_to_ansistr
# [8] end;
leave
ret
.Lc2:
.Le0:
.size P$TCALLCONV_SOMEFUNCTION$PCHAR$LONGWORD$$ANSISTRING, .Le0 -
P$TCALLCONV_SOMEFUNCTION$PCHAR$LONGWORD$$ANSISTRING
=== listing end ===
In general managed types (which a (Ansi)String is) are passed as parameters.
Regards,
Sven
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