Actually xstest.c dosen't call strcmp at all. The relevant code is

xstest.xs:

#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"


MODULE = xstest         PACKAGE = xstest

void
hello()
   CODE:
      printf("Hello, world!\n");
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xstest.c:

/*
 * This file was generated automatically by xsubpp version 1.9508 from
+ the
 * contents of xstest.xs. Do not edit this file, edit xstest.xs instea
+d.
 *
 *      ANY CHANGES MADE HERE WILL BE LOST!
 *
 */

#line 1 "xstest.xs"
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"


#line 16 "xstest.c"
XS(XS_xstest_hello)
{
    dXSARGS;
    if (items != 0)
        Perl_croak(aTHX_ "Usage: xstest::hello()");
    {
#line 11 "xstest.xs"
      printf("Hello, world!\n");
#line 25 "xstest.c"
    }
    XSRETURN_EMPTY;
}

#ifdef __cplusplus
extern "C"
#endif
XS(boot_xstest)
{
    dXSARGS;
    char* file = __FILE__;

    XS_VERSION_BOOTCHECK ;

        newXS("xstest::hello", XS_xstest_hello, file);
    XSRETURN_YES;
}
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