PlatformIO Community

Initializing web-server as a global variable throws this: Clang-Tidy: Initialization of 'server' with static storage duration may throw an exception that cannot be caught

Advanced Solutions Static Code Analysis
#1

First off, I know that this problem is basically a no-brainer, and I should ignore the warning and move on with my day, but what is a science without seemingly meaningless questions answered.

The code runs just fine without me changing anything at the top. Everyone who used the web-server library knows the most efficient way to implement is to:

#include <WebServer.h>
WebServer server;

void setup() {
    server.begin();
}

void loop() {
    server.handleClient();
}

However, I’m interested if it could be declared as non-static/non-global. If it even can happen.

#2

Well you can trigger the constructor execution at different places.

You could e.g. have WebServer *server; and then allocate the object using server = new WebServer(); in setup() and use server->... everywhere. If the constructor throws an exception, you should be able to catch it with try-catch.

Further by using placement new, you can even new the object in a pre-given buffer space (should be sizeof(WebServer) of course), so no actual heap memory is used at all.

Or, allocate the object on the stack of a function and make sure execution never leaves the function; once the variable scope is left, the object is deallocated. You can e.g. allocate it setup(), followed by your own while(true) { own_loop(&server); } loop to make sure execution never leaves setup(). When using anything with a watchdog, you might also need to reset the watchdog if that’s something that’s done by the Arduino core between the execution of loop.

1 Like