use copyBufferAndPad instead of str.fill and std::memcpy

Take copyBufferAndPad out of anonymous namespace and declear
in header file.

Author: Yi Wu

flang/include/flang/Runtime/time-intrinsic.h

@@ -9,6 +9,17 @@
 // Defines the API between compiled code and the implementations of time-related
 // intrinsic subroutines in the runtime library.
 
+// time-intrinsic.h
+#ifndef TIME_INTRINSIC_H
+#define TIME_INTRINSIC_H
+
+#include <cstddef>
+
+void copyBufferAndPad(
+    char *dest, std::size_t destChars, char *buffer, std::size_t len);
+
+#endif // TIME_INTRINSIC_H
+
 #ifndef FORTRAN_RUNTIME_TIME_INTRINSIC_H_
 #define FORTRAN_RUNTIME_TIME_INTRINSIC_H_
 

flang/runtime/extensions.cpp

@@ -14,6 +14,7 @@
 #include "flang/Runtime/command.h"
 #include "flang/Runtime/descriptor.h"
 #include "flang/Runtime/io-api.h"
+#include "flang/Runtime/time-intrinsic.h" // copyBufferAndPad
 #include <ctime>
 
 #ifdef _WIN32
@@ -47,24 +48,21 @@ void FORTRAN_PROCEDURE_NAME(flush)(const int &unit) {
 std::int32_t FORTRAN_PROCEDURE_NAME(iargc)() { return RTNAME(ArgumentCount)(); }
 
 void FORTRAN_PROCEDURE_NAME(fdate)(std::int8_t *arg, std::int64_t length) {
-  std::array<char, 26> str;
   // If the length is too short to fit completely, blank return.
   if (length < 24) {
-    str.fill(' ');
-    strncpy(reinterpret_cast<char *>(arg), str.data(), length);
+    copyBufferAndPad(reinterpret_cast<char *>(arg), length, nullptr, 0);
     return;
   }
 
+  std::array<char, 26> str;
   Terminator terminator{__FILE__, __LINE__};
   std::time_t current_time;
   std::time(&current_time);
   // Day Mon dd hh:mm:ss yyyy\n\0 is 26 characters, e.g.
   // Tue May 26 21:51:03 2015\n\0
 
   ctime_alloc(str.data(), str.size(), current_time, terminator);
-
-  std::fill(str.begin() + 24, str.begin() + length, ' ');
-  strncpy(reinterpret_cast<char *>(arg), str.data(), length);
+  copyBufferAndPad(reinterpret_cast<char *>(arg), length, str.data(), 24);
 }
 
 // CALL GETARG(N, ARG)

flang/runtime/time-intrinsic.cpp

@@ -39,6 +39,16 @@
 // overload will have a dummy parameter whose type indicates whether or not it
 // should be preferred. Any other parameters required for SFINAE should have
 // default values provided.
+
+void copyBufferAndPad(
+    char *dest, std::size_t destChars, char *buffer, std::size_t len) {
+  auto copyLen{std::min(len, destChars)};
+  std::memcpy(dest, buffer, copyLen);
+  for (auto i{copyLen}; i < destChars; ++i) {
+    dest[i] = ' ';
+  }
+}
+
 namespace {
 // Types for the dummy parameter indicating the priority of a given overload.
 // We will invoke our helper with an integer literal argument, so the overload
@@ -279,29 +289,21 @@ static void GetDateAndTime(Fortran::runtime::Terminator &terminator, char *date,
 
   static constexpr std::size_t buffSize{16};
   char buffer[buffSize];
-  auto copyBufferAndPad{
-      [&](char *dest, std::size_t destChars, std::size_t len) {
-        auto copyLen{std::min(len, destChars)};
-        std::memcpy(dest, buffer, copyLen);
-        for (auto i{copyLen}; i < destChars; ++i) {
-          dest[i] = ' ';
-        }
-      }};
   if (date) {
     auto len = std::strftime(buffer, buffSize, "%Y%m%d", &localTime);
-    copyBufferAndPad(date, dateChars, len);
+    copyBufferAndPad(date, dateChars, buffer, len);
   }
   if (time) {
     auto len{std::snprintf(buffer, buffSize, "%02d%02d%02d.%03jd",
         localTime.tm_hour, localTime.tm_min, localTime.tm_sec, ms)};
-    copyBufferAndPad(time, timeChars, len);
+    copyBufferAndPad(time, timeChars, buffer, len);
   }
   if (zone) {
     // Note: this may leave the buffer empty on many platforms. Classic flang
     // has a much more complex way of doing this (see __io_timezone in classic
     // flang).
     auto len{std::strftime(buffer, buffSize, "%z", &localTime)};
-    copyBufferAndPad(zone, zoneChars, len);
+    copyBufferAndPad(zone, zoneChars, buffer, len);
   }
   if (values) {
     auto typeCode{values->type().GetCategoryAndKind()};