Passing parameters to a C function

<div class="Section1"><p class="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt;
font-family:Arial">    Hello,</span></font><p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size:10.0pt;
font-family:Arial"> </span></font><p class="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt;
font-family:Arial">   I have a question about passing parameters to a C function.  Imagine the example by
PostgreSQL:</span></font><pclass="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt; 
font-family:Arial"> </span></font><p class="MsoNormal" style="margin-left:.5in"><font face="Courier New" size="2"><span
style="font-size:10.0pt;font-family:"CourierNew"">PG_FUNCTION_INFO_V1(complex_add);</span></font><p class="MsoNormal"
style="margin-left:.5in"><fontface="Courier New" size="2"><span style="font-size:10.0pt;font-family:"Courier
New""> </span></font><pclass="MsoNormal" style="margin-left:.5in"><font face="Courier New" size="2"><span
style="font-size:10.0pt;font-family:"CourierNew"">Datum</span></font><p class="MsoNormal"
style="margin-left:.5in"><fontface="Courier New" size="2"><span style="font-size:10.0pt;font-family:"Courier
New"">complex_add(PG_FUNCTION_ARGS)</span></font><pclass="MsoNormal" style="margin-left:.5in"><font face="Courier New"
size="2"><spanstyle="font-size:10.0pt;font-family:"Courier New"">{</span></font><p class="MsoNormal"
style="margin-left:.5in"><fontface="Courier New" size="2"><span style="font-size:10.0pt;font-family:"Courier
New"">     Complex    *a = (Complex *) PG_GETARG_POINTER(0);</span></font><p class="MsoNormal"
style="margin-left:.5in"><fontface="Courier New" size="2"><span style="font-size:10.0pt;font-family:"Courier
New"">     Complex    *b = (Complex *) PG_GETARG_POINTER(1);</span></font><p class="MsoNormal"
style="margin-left:.5in"><fontface="Courier New" size="2"><span style="font-size:10.0pt;font-family:"Courier
New"">     Complex    *result;</span></font><p class="MsoNormal" style="margin-left:.5in"><font face="Courier New"
size="2"><spanstyle="font-size:10.0pt;font-family:"Courier New""> </span></font><p class="MsoNormal"
style="margin-left:.5in"><fontface="Courier New" size="2"><span style="font-size:10.0pt;font-family:"Courier
New"">     result = (Complex *) palloc(sizeof(Complex));</span></font><p class="MsoNormal"
style="margin-left:.5in"><fontface="Courier New" size="2"><span style="font-size:10.0pt;font-family:"Courier
New"">     result->x = a->x + b->x;</span></font><p class="MsoNormal" style="margin-left:.5in"><font
face="CourierNew" size="2"><span style="font-size:10.0pt;font-family:"Courier New"">      result->y = a->y +
b->y;</span></font><pclass="MsoNormal" style="margin-left:.5in"><font face="Courier New" size="2"><span
style="font-size:10.0pt;font-family:"CourierNew"">      PG_RETURN_POINTER(result);</span></font><p class="MsoNormal"
style="margin-left:.5in"><fontface="Courier New" size="2"><span style="font-size:10.0pt;font-family:"Courier
New"">}</span></font><pclass="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt; 
font-family:Arial"> </span></font><p class="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt;
font-family:Arial"> So, in the same .C file I have to write another function that calls this one, for example:
</span></font><pclass="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt; 
font-family:Arial"> </span></font><p class="MsoNormal" style="margin-left:.5in"><font face="Courier New" size="2"><span
style="font-size:10.0pt;font-family:"CourierNew"">void</span></font><p class="MsoNormal" style="margin-left:.5in"><font
face="CourierNew" size="2"><span style="font-size:10.0pt;font-family:"Courier New"">test_main()</span></font><p
class="MsoNormal"style="margin-left:.5in"><font face="Courier New" size="2"><span
style="font-size:10.0pt;font-family:"CourierNew"">{</span></font><p class="MsoNormal" style="margin-left:.5in"><font
face="CourierNew" size="2"><span style="font-size:10.0pt;font-family:"Courier New"">    Complex *a;</span></font><p
class="MsoNormal"style="margin-left:.5in"><font face="Courier New" size="2"><span
style="font-size:10.0pt;font-family:"CourierNew"">    Complex *b;</span></font><p class="MsoNormal"
style="margin-left:.5in"><fontface="Courier New" size="2"><span style="font-size:10.0pt;font-family:"Courier
New""> </span></font><pclass="MsoNormal" style="margin-left:.5in"><font face="Courier New" size="2"><span
style="font-size:10.0pt;font-family:"CourierNew"">    a = complex_in("(4.01, 3.77 )");</span></font><p
class="MsoNormal"style="margin-left:.5in"><font face="Courier New" size="2"><span
style="font-size:10.0pt;font-family:"CourierNew"">    printf("a = %s\n", complex_out(a));</span></font><p
class="MsoNormal"style="margin-left:.5in"><font face="Courier New" size="2"><span
style="font-size:10.0pt;font-family:"CourierNew""> </span></font><p class="MsoNormal" style="margin-left:.5in"><font
face="CourierNew" size="2"><span style="font-size:10.0pt;font-family:"Courier New"">    b =
complex_in("(1.0,2.0)");</span></font><pclass="MsoNormal" style="margin-left:.5in"><font face="Courier New"
size="2"><spanstyle="font-size:10.0pt;font-family:"Courier New"">    printf("b = %s\n",
complex_out(b));</span></font><pclass="MsoNormal" style="margin-left:.5in"><font face="Courier New" size="2"><span
style="font-size:10.0pt;font-family:"CourierNew""> </span></font><p class="MsoNormal" style="margin-left:.5in"><font
face="CourierNew" size="2"><span style="font-size:10.0pt;font-family:"Courier New"">    printf("a +  b = %s\n",
complex_out(complex_add(a,b)));</span></font><pclass="MsoNormal" style="margin-left:.5in"><font face="Courier New"
size="2"><spanstyle="font-size:10.0pt;font-family:"Courier New"">}</span></font><p class="MsoNormal"
style="margin-left:.5in"><fontface="Courier New" size="2"><span style="font-size:10.0pt;font-family:"Courier
New""> </span></font><pclass="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt; 
font-family:Arial">But using version 1 calling convention it won’t work! So, how can I pass the ‘a’ and ‘b’ variables
incomplex_add(?, ?)?</span></font><p class="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt; 
font-family:Arial"> </span></font><p class="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt;
font-family:Arial">Thanks in advance!</span></font><p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size:10.0pt;
font-family:Arial"> </span></font><p class="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt;
font-family:Arial"> </span></font><p class="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt;
font-family:Arial"> </span></font><p class="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt;
font-family:Arial"> </span></font></div>