configure: Support MSVC 2015

The C runtime C99 compatibility had been improved a lot and it now
rejects some of the compatibility defines provided for the older
versions.

Many thanks to Ray for the time spent testing.

Bug-Id: 864
CC: libav-stable@libav.org

configure

@@ -3021,9 +3021,6 @@ probe_cc(){
         _ld_path='-libpath:'
         _flags='-nologo'
         _cflags='-D_USE_MATH_DEFINES -D_CRT_SECURE_NO_WARNINGS -Dinline=__inline -FIstdlib.h -Dstrtoll=_strtoi64'
-        if [ $pfx = hostcc ]; then
-            append _cflags -Dsnprintf=_snprintf
-        fi
     elif $_cc 2>&1 | grep -q Intel; then
         _type=icl
         _ident=$($_cc 2>&1 | head -n1)
@@ -3047,9 +3044,6 @@ probe_cc(){
         # -Qvec- -Qsimd- to prevent miscompilation, -GS for consistency
         # with MSVC which enables it by default.
         _cflags='-D_USE_MATH_DEFINES -FIstdlib.h -Dstrtoll=_strtoi64 -Qms0 -Qvec- -Qsimd- -GS'
-        if [ $pfx = hostcc ]; then
-            append _cflags -Dsnprintf=_snprintf
-        fi
     elif $_cc --version 2>/dev/null | grep -q ^cparser; then
         _type=cparser
         _ident=$($_cc --version | head -n1)
@@ -3743,6 +3737,16 @@ probe_libc(){
             add_${pfx}cppflags -D__printf__=__gnu_printf__
     elif check_${pfx}cpp_condition crtversion.h "defined _VC_CRT_MAJOR_VERSION"; then
         eval ${pfx}libc_type=msvcrt
+        if check_${pfx}cpp_condition crtversion.h "_VC_CRT_MAJOR_VERSION < 14"; then
+            if [ "$pfx" = host_ ]; then
+                add_host_cppflags -Dsnprintf=_snprintf
+            else
+                add_compat strtod.o strtod=avpriv_strtod
+                add_compat msvcrt/snprintf.o snprintf=avpriv_snprintf   \
+                                             _snprintf=avpriv_snprintf  \
+                                             vsnprintf=avpriv_vsnprintf
+            fi
+        fi
         # The MSVC 2010 headers (Win 7.0 SDK) set _WIN32_WINNT to
         # 0x601 by default unless something else is set by the user.
         # This can easily lead to us detecting functions only present
@@ -3773,12 +3777,6 @@ case $libc_type in
     bionic)
         add_compat strtod.o strtod=avpriv_strtod
         ;;
-    msvcrt)
-        add_compat strtod.o strtod=avpriv_strtod
-        add_compat msvcrt/snprintf.o snprintf=avpriv_snprintf   \
-                                     _snprintf=avpriv_snprintf  \
-                                     vsnprintf=avpriv_vsnprintf
-        ;;
 esac
 
 # hacks for compiler/libc/os combinations

libavutil/internal.h

@@ -130,11 +130,6 @@
 
 #include "libm.h"
 
-#if defined(_MSC_VER)
-#pragma comment(linker, "/include:"EXTERN_PREFIX"avpriv_strtod")
-#pragma comment(linker, "/include:"EXTERN_PREFIX"avpriv_snprintf")
-#endif
-
 /**
  * Return NULL if CONFIG_SMALL is true, otherwise the argument
  * without modification. Used to disable the definition of strings
@@ -208,6 +203,12 @@ void avpriv_request_sample(void *avc,
                            const char *msg, ...) av_printf_format(2, 3);
 
 #if HAVE_LIBC_MSVCRT
+#include <crtversion.h>
+#if defined(_VC_CRT_MAJOR_VERSION) && _VC_CRT_MAJOR_VERSION < 14
+#pragma comment(linker, "/include:"EXTERN_PREFIX"avpriv_strtod")
+#pragma comment(linker, "/include:"EXTERN_PREFIX"avpriv_snprintf")
+#endif
+
 #define avpriv_open ff_open
 #endif