Add support of string_t by M_PRINT macro.

m-core.h

@@ -1872,7 +1872,10 @@ M_BEGIN_PROTECTED_CODE
            const char *: "%s",                                                \
            char *: "%s",                                                      \
            const void *: "%p",                                                \
-           void *: "%p")
+           void *: "%p"                                                       \
+           M_PRINTF_FORMAT_EXTEND() )
+
+#define M_PRINTF_FORMAT_EXTEND() /* Nothing in m-core (see m-string.h) */
 
 /* IF FILE is supported */
 #if M_USE_STDIO
@@ -1937,11 +1940,14 @@ m_core_fopen(const char filename[], const char opt[])
 
 #endif
 
+/* Can be overloaded by m-string to support string output too */
+#define M_CORE_PRINTF_ARG(x) x
+
 /* Print a C variable if it is a standard type to stdout.*/
-#define M_PRINT_ARG(x) printf(M_PRINTF_FORMAT(x), x)
+#define M_PRINT_ARG(x) printf(M_PRINTF_FORMAT(x), M_CORE_PRINTF_ARG(x) )
 
 /* Print a C variable if it is a standard type to the given file 'f'.*/
-#define M_FPRINT_ARG(f, x) fprintf(f, M_PRINTF_FORMAT(x), x)
+#define M_FPRINT_ARG(f, x) fprintf(f, M_PRINTF_FORMAT(x), M_CORE_PRINTF_ARG(x))
 
 /* Get a C variable if it is a standard type from the given file 'f'.*/
 #define M_FSCAN_ARG(xptr, f)                                                  \
@@ -2007,7 +2013,7 @@ M_FSCAN_DEFAULT_TYPE_DEF(m_core_fscan_ldouble, long double, "%Lf")
 
 /* Transform a C variable into a string_t (needs m-string.h) */
 #define M_GET_STRING_ARG(str, x, append)                                      \
-  (append ? string_cat_printf : string_printf) (str, M_PRINTF_FORMAT(x), x)
+  (append ? string_cat_printf : string_printf) (str, M_PRINTF_FORMAT(x), M_CORE_PRINTF_ARG(x))
 
 /* No use of GET_STR if no inclusion of m-string */
 #define M_GET_STR_METHOD_FOR_DEFAULT_TYPE /* */
@@ -3182,7 +3188,7 @@ m_core_parse2_enum (const char str[], const char **endptr)
 /* Return the content of a property named 'propname' 
    in the PROPERTIES field of oplist
    or 0, if it is not defined */
-#define M_GET_OPPROPERTY(oplist, propname)                     \
+#define M_GET_OPPROPERTY(oplist, propname)                                    \
   M_GET_METHOD (propname, 0, M_OPFLAT M_GET_PROPERTIES oplist)
 
 /* Test if a method is present in an oplist.

m-string.h

@@ -1906,10 +1906,27 @@ namespace m_lib {
   M_APPLY(M_STRING_SELECT3, string_search, string_search_str,                 \
           v, M_IF_DEFAULT1(0, __VA_ARGS__))
 
+/**************** Override m-core default macros to add support of string_t ******/
+
 /* Internal Macro: Provide GET_STR method to default type */
 #undef M_GET_STR_METHOD_FOR_DEFAULT_TYPE
 #define M_GET_STR_METHOD_FOR_DEFAULT_TYPE GET_STR(M_GET_STRING_ARG)
 
+/* Internal Macro: Provide support of string_t to the macro M_PRINT in C11 */
+
+// Extend the format specifier to support string_t
+#undef M_PRINTF_FORMAT_EXTEND
+#define M_PRINTF_FORMAT_EXTEND()                                              \
+          , string_ptr: "%s"                                                  \
+          , string_srcptr: "%s"
+
+// Add type conversion for string_t (into a const char*)
+#undef M_CORE_PRINTF_ARG
+#define M_CORE_PRINTF_ARG(x) _Generic( ((void)0,(x))                          \
+          , string_ptr: string_get_cstr( M_AS_TYPE(string_ptr, x))            \
+          , string_srcptr: string_get_cstr(M_AS_TYPE(string_srcptr,x))        \
+          , default: x )
+
 #endif
 
 /* Internal Macro: Provide GET_STR method to enum type */
@@ -1918,6 +1935,7 @@ namespace m_lib {
 
 
 
+
 /***********************************************************************/
 /*                                                                     */
 /*                BOUNDED STRING, aka char[N+1]                        */