fixes #23304; uses snprintf instead of sprintf (#23322)

fixes #23304

(cherry picked from commit dfd778d056)

lib/system/ansi_c.nim

@@ -187,6 +187,9 @@ proc c_sprintf*(buf, frmt: cstring): cint {.
   importc: "sprintf", header: "<stdio.h>", varargs, noSideEffect.}
   # we use it only in a way that cannot lead to security issues
 
+proc c_snprintf*(buf: cstring, n: csize_t, frmt: cstring): cint {.
+  importc: "snprintf", header: "<stdio.h>", varargs, noSideEffect.}
+
 when defined(zephyr) and not defined(zephyrUseLibcMalloc):
   proc c_malloc*(size: csize_t): pointer {.
     importc: "k_malloc", header: "<kernel.h>".}

lib/system/repr.nim

@@ -17,7 +17,7 @@ proc reprFloat(x: float): string {.compilerproc.} = return $x
 
 proc reprPointer(x: pointer): string {.compilerproc.} =
   result = newString(60)
-  let n = c_sprintf(cast[cstring](addr result[0]), "%p", x)
+  let n = c_snprintf(cast[cstring](addr result[0]), csize_t(60), "%p", x)
   setLen(result, n)
 
 proc reprStrAux(result: var string, s: cstring; len: int) =