sendHeader & F()

[bstsoftorg]

Basic Infos

To the developers:
Initially encountered a problem when using sendHeader, but this is true of many places.
There is a shortage of memory. Once stood 2.3.0-rc2, decided to move to 2.4.0, which was better, but some places are still eating RAM.
Possible enclose strings in F(). And not only where I point out in other places too.

Hardware

Hardware: ESP-12F
Core Version: 2.3.0-rc2, 2.4.0

Description

ESP8266WebServer.cpp
Global variables used 41524 bytes (50%) of dynamic memory, leaving 40396 bytes for local variables.
_srealm = F("Login Required");
Global variables used 41508 bytes (50%) of dynamic memory, leaving 40412 bytes for local variables.

Global variables used 41524 bytes (50%) of dynamic memory, leaving 40396 bytes for local variables.
sendHeader("WWW-Authenticate", String() + F("Basic realm="") + _srealm + F("""));
Global variables used 41508 bytes (50%) of dynamic memory, leaving 40412 bytes for local variables.

ESP8266HTTPClient.cpp
Global variables used 41524 bytes (50%) of dynamic memory, leaving 40396 bytes for local variables.
if (!beginInternal(url, String(F("https")).c_str())) {
Global variables used 41508 bytes (50%) of dynamic memory, leaving 40412 bytes for local variables.

Global variables used 41524 bytes (50%) of dynamic memory, leaving 40396 bytes for local variables.
if (!beginInternal(url, String(F("http")).c_str())) {
Global variables used 41508 bytes (50%) of dynamic memory, leaving 40412 bytes for local variables.

[devyte]

Closing via #4148 which already merged.