'Reallocating large String(... -> ...)' warning when using WebServer

[hmueller01]

Hi,

since PR #8821 I get this output from ESP8266WebServer:

[String] 'Content-Ty ... ires: -1
': Reallocating large String(140 -> 162 bytes)

It's from this line

Arduino/libraries/ESP8266WebServer/src/ESP8266WebServer-impl.h

Line 433 in be02af0

_responseHeaders += headerLine;

if sendHeader() is used more than once. Like here:
https://github.com/khoih-prog/ESP_WiFiManager_Lite/blob/085afdbd7ccfb7e46b1ed9f1cf5c50be29cc3223/src/ESP_WiFiManager_Lite.h#L2771

Is there something we can do against it?

[d-a-v]

Thanks for having revealed an internal misuse of strings.
Fixing this is on us.

[d-a-v]

If you are using the git version of this core, can you try with #8873 ?

(or the unofficial "nightly" alpha release)

[hmueller01]

As written in #8873 the change in ESP8266WebServer looks good to me.

There is similar issue in ESP8266HTTPClient

Arduino/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.cpp

Line 820 in 6ad9bf3

_headers += headerLine;

if you add multiple headers ...

[mathertel]

The output appears also in the published version 3.1.2 when DEBUG_ESP_PORT is enabled even when Debug Level == none.

Example:

[String] 'Content-Ty ... rigin: *
': Reallocating large String(159 -> 183 bytes)
[String] 'Content-Ty ... ep-alive
': Reallocating large String(183 -> 209 bytes)