msvcrt: Fix precision handling for string arguments.

dlls/msvcrt/msvcrt.h

@@ -1094,6 +1094,8 @@ char*** __cdecl  MSVCRT___p__environ(void);
 int*    __cdecl  __p___mb_cur_max(void);
 unsigned int*  __cdecl __p__fmode(void);
 MSVCRT_wchar_t* __cdecl MSVCRT__wcsdup(const MSVCRT_wchar_t*);
+MSVCRT_size_t __cdecl MSVCRT_strnlen(const char *,MSVCRT_size_t);
+MSVCRT_size_t __cdecl MSVCRT_wcsnlen(const MSVCRT_wchar_t*,MSVCRT_size_t);
 MSVCRT_wchar_t*** __cdecl MSVCRT___p__wenviron(void);
 INT     __cdecl MSVCRT_wctomb(char*,MSVCRT_wchar_t);
 char*   __cdecl MSVCRT__strdate(char* date);

dlls/msvcrt/printf.h

@@ -165,8 +165,13 @@ static inline int FUNC_NAME(pf_output_format_wstr)(FUNC_NAME(puts_clbk) pf_puts,
 {
     int r, ret;
 
-    if(len < 0)
+    if(len < 0) {
+        /* Do not search past the length specified by the precision. */
+        if(flags->Precision>=0)
+            len = MSVCRT_wcsnlen(str, flags->Precision);
+        else
             len = strlenW(str);
+    }
 
     if(flags->Precision>=0 && flags->Precision<len)
         len = flags->Precision;
@@ -190,8 +195,13 @@ static inline int FUNC_NAME(pf_output_format_str)(FUNC_NAME(puts_clbk) pf_puts,
 {
     int r, ret;
 
-    if(len < 0)
+    if(len < 0) {
+        /* Do not search past the length specified by the precision. */
+        if(flags->Precision>=0)
+            len = MSVCRT_strnlen(str, flags->Precision);
+        else
             len = strlen(str);
+    }
 
     if(flags->Precision>=0 && flags->Precision<len)
         len = flags->Precision;