Library internally uses deprecated function beginResponse_P causing compile warnings on ESP8266

[pdfelen]

Platform

ESP8266

IDE / Tooling

Arduino (IDE/CLI)

What happened?

In version 3.12.1 beginResponse_P has been depricated, however in ESPAsyncWebServer.h line 717 it internally still uses beginResponse_P causing compiler warnings:
c:.....\ESP_Async_WebServer\src/ESPAsyncWebServer.h:717:62: warning: 'AsyncWebServerResponse* AsyncWebServerRequest::beginResponse_P(int, const String&, const char*, AwsTemplateProcessor)' is deprecated: Replaced by beginResponse(int code, const String& contentType, const char* content = asyncsrv::empty, AwsTemplateProcessor callback = nullptr) [-Wdeprecated-declarations]

717 | send(beginResponse_P(code, contentType, content, callback));

  |                                                              ^

c:\Pepijn\Projecten\Elektronica\Source\libraries\ESP_Async_WebServer\src/ESPAsyncWebServer.h:777:27: note: declared here

777 | AsyncWebServerResponse *beginResponse_P(int code, const String &contentType, PGM_P content, AwsTemplateProcessor callback = nullptr);

  |                           ^~~~~~~~~~~~~~~

Replacing beginResponse_P on line 717 for beginResponse will make the warnings go away.

Stack Trace

No crash, compile warning for ESP8266

Minimal Reproductible Example (MRE)

Compile warning for ESP8266

I confirm that:

• I have read the documentation.
• I have searched for similar discussions.
• I have searched for similar issues.
• I have looked at the examples.
• I have upgraded to the lasted version of ESPAsyncWebServer (and AsyncTCP for ESP32).

[mathieucarbou]

Hi,
I suspect you are using 8266 code but compile / use it with esp32 ? It you are just compiling on 8266 platform only ?

[mathieucarbou]

I am converting this to a discussion because this is not an issue, and the solution to such warning might be more complicated.

The redirection is not right because the PGM_P type is lost, and PGM_P could be something else than a const char*

[mathieucarbou]

Right but doing that is wrong: send(beginResponse(

content is of type PGM_P (can be a flash string on 8266).

if you redirect to beginResponse (which does not support 8266 flash string PGM_P), then your string will be put on heap as a const char*.

I will verify: that's possible that the PGM_P macro now has changed - I never use 8266 - the code (and fixes) are mostly user contribs.

[pdfelen]

Thanks for the quick response by the way.
Understood. For me it is working in my application. I can understand, as you describe, there are cases it will not work.
But then I think there still needs to be an issue open to track solving the warning messages.

Is it an option to exclude the deprecated message for beginResponse_P for ESP8266? Because that can also remove the warnings...

[mathieucarbou]

See here: #490 (comment)

Another explanation why the change is wrong:

• beginResponse_P creates a return new AsyncProgmemResponse(code, contentType, (const uint8_t *)content, strlen_P(content), callback); => the content is a pointer to a flash string
• beginResponse creates a return new AsyncBasicResponse(code, contentType, content); => the content is a COPY ON HEAP of the const char pointer*

So what you'll end up doing with this change is exhausting your heap memory.

Check the implementation to see what the code does under the hood.

[mathieucarbou]

On ESP8266, we have::

  void send_P(int code, const String &contentType, PGM_P content, AwsTemplateProcessor callback = nullptr) {
    send(beginResponse_P(code, contentType, content, callback));
  }
  
  [[deprecated("Replaced by beginResponse(int code, const String& contentType, const uint8_t* content, size_t len, AwsTemplateProcessor callback = nullptr)")]]
  AsyncWebServerResponse *beginResponse_P(int code, const String &contentType, const uint8_t *content, size_t len, AwsTemplateProcessor callback = nullptr) {
    return beginResponse(code, contentType.c_str(), content, len, callback);
  }
  [[deprecated("Replaced by beginResponse(int code, const String& contentType, const char* content = asyncsrv::empty, AwsTemplateProcessor callback = nullptr)"
  )]]
  AsyncWebServerResponse *beginResponse_P(int code, const String &contentType, PGM_P content, AwsTemplateProcessor callback = nullptr);

What indeed can be done is removing the deprecation on 8266.

[mathieucarbou]

@pdfelen this is the right fix: #492

[pdfelen]

Hi Mathieu,
I understand your point. Point taken.
I already checked that, it removes the warnings indeed and is working also.

Around 717:
#else // ESP8266 code
void send_P(int code, const String &contentType, PGM_P content, AwsTemplateProcessor callback = nullptr) {
send(beginResponse_P(code, contentType, content, callback)); //<-- reverted back
}

Around 777:
#ifndef ESP8266
[[deprecated("Replaced by beginResponse(int code, const String& contentType, const uint8_t* content, size_t len, AwsTemplateProcessor callback = nullptr)")]]
#endif
AsyncWebServerResponse *beginResponse_P(int code, const String &contentType, const uint8_t content, size_t len, AwsTemplateProcessor callback = nullptr) {
return beginResponse(code, contentType.c_str(), content, len, callback);
}
#ifndef ESP8266
[[deprecated("Replaced by beginResponse(int code, const String& contentType, const char content = asyncsrv::empty, AwsTemplateProcessor callback = nullptr)"
)]]
#endif
AsyncWebServerResponse *beginResponse_P(int code, const String &contentType, PGM_P content, AwsTemplateProcessor callback = nullptr);

Do you want me to commit this?

[mathieucarbou]

check the pull request: this should fix the warning: #492 ;-)

[pdfelen]

OK thanks. I'll see it in the next release update.
Thanks for continuing this library. Great job.