Call snprintf when available in posix_api.cpp.

Fixes https://github.com/boostorg/regex/issues/184.

include/boost/regex/v5/icu.hpp

@@ -190,8 +190,8 @@ public:
       constexpr char_class_type mask_xdigit = char_class_type(1) << offset_xdigit;
       constexpr char_class_type mask_underscore = char_class_type(1) << offset_underscore;
       constexpr char_class_type mask_unicode = char_class_type(1) << offset_unicode;
-      constexpr char_class_type mask_any = char_class_type(1) << offset_any;
-      constexpr char_class_type mask_ascii = char_class_type(1) << offset_ascii;
+      //constexpr char_class_type mask_any = char_class_type(1) << offset_any;
+      //constexpr char_class_type mask_ascii = char_class_type(1) << offset_ascii;
       constexpr char_class_type mask_horizontal = char_class_type(1) << offset_horizontal;
       constexpr char_class_type mask_vertical = char_class_type(1) << offset_vertical;
 
@@ -365,15 +365,15 @@ private:
 
    static char_class_type lookup_icu_mask(const ::UChar32* p1, const ::UChar32* p2)
    {
-      constexpr char_class_type mask_blank = char_class_type(1) << offset_blank;
-      constexpr char_class_type mask_space = char_class_type(1) << offset_space;
-      constexpr char_class_type mask_xdigit = char_class_type(1) << offset_xdigit;
-      constexpr char_class_type mask_underscore = char_class_type(1) << offset_underscore;
-      constexpr char_class_type mask_unicode = char_class_type(1) << offset_unicode;
+      //constexpr char_class_type mask_blank = char_class_type(1) << offset_blank;
+      //constexpr char_class_type mask_space = char_class_type(1) << offset_space;
+      //constexpr char_class_type mask_xdigit = char_class_type(1) << offset_xdigit;
+      //constexpr char_class_type mask_underscore = char_class_type(1) << offset_underscore;
+      //constexpr char_class_type mask_unicode = char_class_type(1) << offset_unicode;
       constexpr char_class_type mask_any = char_class_type(1) << offset_any;
       constexpr char_class_type mask_ascii = char_class_type(1) << offset_ascii;
-      constexpr char_class_type mask_horizontal = char_class_type(1) << offset_horizontal;
-      constexpr char_class_type mask_vertical = char_class_type(1) << offset_vertical;
+      //constexpr char_class_type mask_horizontal = char_class_type(1) << offset_horizontal;
+      //constexpr char_class_type mask_vertical = char_class_type(1) << offset_vertical;
 
       static const ::UChar32 prop_name_table[] = {
          /* any */  'a', 'n', 'y',

src/posix_api.cpp

@@ -21,6 +21,7 @@
 #include <boost/config.hpp>
 #include <boost/regex.hpp>
 #include <boost/cregex.hpp>
+#include <boost/cstdint.hpp>
 #include <cstdio>
 
 #if defined(BOOST_NO_STDC_NAMESPACE)
@@ -176,7 +177,9 @@ BOOST_REGEX_DECL regsize_t BOOST_REGEX_CCALL regerrorA(int code, const regex_tA*
             // We're converting an integer i to a string, and since i <= REG_E_UNKNOWN
             // a five character string is *always* large enough:
             //
-#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400) && !defined(_WIN32_WCE) && !defined(UNDER_CE)
+#if BOOST_CXX_VERSION >= 201103
+            int r = (std::snprintf)(localbuf, 5, "%d", i);
+#elif BOOST_WORKAROUND(BOOST_MSVC, >= 1400) && !defined(_WIN32_WCE) && !defined(UNDER_CE)
             int r = (::sprintf_s)(localbuf, 5, "%d", i);
 #else
             int r = (std::sprintf)(localbuf, "%d", i);
@@ -188,7 +191,9 @@ BOOST_REGEX_DECL regsize_t BOOST_REGEX_CCALL regerrorA(int code, const regex_tA*
             return std::strlen(localbuf) + 1;
          }
       }
-#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400) && !defined(_WIN32_WCE) && !defined(UNDER_CE)
+#if BOOST_CXX_VERSION >= 201103
+      int r = (::snprintf)(localbuf, 5, "%d", 0);
+#elif BOOST_WORKAROUND(BOOST_MSVC, >= 1400) && !defined(_WIN32_WCE) && !defined(UNDER_CE)
       int r = (::sprintf_s)(localbuf, 5, "%d", 0);
 #else
       int r = (std::sprintf)(localbuf, "%d", 0);

src/wide_posix_api.cpp

@@ -24,6 +24,7 @@
 
 #include <boost/regex.hpp>
 #include <boost/cregex.hpp>
+#include <boost/cstdint.hpp>
 
 #include <cstdio>
 #include <cstring>