[Vxl-maintainers] sqrtf and msvc++

[Wheeler, F. (Research) <wh...@cr...>]

Peter,

My msvc++ build is not finding _sqrtf.

It looks to me like sqrtf is available with MSVC++ (C++), but not MSVC (C).  My test code is below,
with comments telling which commands worked and which did not.

MSVC++ math.h declares sqrtf only when __cplusplus is set.

I have not been able to get a decent explanation from MSDN on this sqrtf issue.  MSDN does not
clearly distinguish between C and C++.  According to MSDN, MSVC++ decides whether to link in standard
C++ libraries, or to just link in standard C libraries based on what header files a program includes.
So, from MSDN I can't tell what it is doing with mixed C/C++ to figure out whether a C program could
use sqrtf from the C++ lib.

I think VXL_MATH_HAS_SQRTF should not be set under MSVC.  Do you agree?

Fred Wheeler


-- hello.cxx ----------------------------------------------

/*

g++ -c hello.cxx -o hello.o
# works fine
g++ hello.o -o hello
# works fine
./hello
# works fine

cl /nologo /GX hello.cxx /Fohello.obj
# works fine
cl /nologo /GX hello.obj /Fehello.exe
# works fine
./hello
# works fine

rm -f hello.exe hello.o hello.obj

*/

#include <iostream>
#include <cmath>

int main ()
{
  std::cout << "Hello" << std::endl;
  std::cout << "sqrtf(2) = " << sqrtf(2.0) << std::endl;
  return 0;
}

-- hello.c ---------------------------------------------------------

/*

gcc -c hello.c -o hello.o
# works fine
gcc hello.o -o hello
# works fine
./hello
# works fine

cl /nologo /W3 /Zm1000 /MD /O2 -c hello.c /Fohello.obj
# warning C4013: 'sqrtf' undefined
cl /nologo /GX hello.obj /Fehello.exe
# error LNK2001: unresolved external symbol _sqrtf
./hello
# not created

rm -f hello.exe hello.o hello.obj

*/

#include <stdio.h>
#include <math.h>

int main ()
{
  printf("Hello\n");
  printf("sqrtf(2) = %g\n", sqrtf(2.0));
  return 0;
}

-------------------------------------------------------------------

--
Fred Wheeler, GE CRD, KWC-303
Phone: 518-387-7225 (GE Internal Dialcom: 8*833-7225)
Fax:   518-387-4042 (GE Internal Dialcom: 8*833-4042)