Support for constraint environment

[elazarl]

Hi,

cppformat is a breath of fresh air, especially when you use it for embedded device where stupid errors could be costly.

Do you plan to make a subset of cppformat available for more constraint environment?

Specifically:

1. Ability to turn off POSIX error handling. I don't have stderr, I only have serial.
2. Ability to turn off classes that requires dynamic memory allocation - stack based alternative for MemoryWriter, and ability to turn off support for basic_string.
3. Ability to turn off wchar support, which is not always available, and not always cost-effective to implement.
4. Ability to use custom printing function, without requiring user to take all the c++ streams abstraction.

Would you accept pull requests in this direction?

[vitaut]

Hi,

Thank you for the nice feedback.

Do you plan to make a subset of cppformat available for more constraint environment?

No, I don't have any plans specifically targeting constrained environments.

[1] Ability to turn off POSIX error handling. I don't have stderr, I only have serial.

I'm not sure what you mean by that. The errors are reported as exceptions, but you can provide your own error handling mechanism via FMT_THROW.

[2] Ability to turn off classes that requires dynamic memory allocation - stack based alternative for MemoryWriter, and ability to turn off support for basic_string.

I think turning off classes with dynamic memory allocation completely via conditional compilation will be too messy, but writing to a fixed, possibly stack-allocated, array is already supported:

char buffer[100];
fmt::ArrayWriter w(buffer);
w.write("The answer is {}", 42);

This could be wrapped in a function for even easier use:

char buffer[100];
format_array(buffer, "The answer is {}", 42);

[3] Ability to turn off wchar support, which is not always available, and not always cost-effective to implement.

Again, I think it would be too messy to turn off completely, but it doesn't add any overhead if you don't use it.

[4] Ability to use custom printing function, without requiring user to take all the c++ streams abstraction.

IOStreams are already optional and only used when formatting types that provide an overloaded ostream operator<<. You can provide a custom formatting function by overloading format instead:

void format(Formatter &f, const char *&format_str, const MyType &value) {
  // parse format_str and format value
}

I'm also open to pull requests that improve support for such environments provided that they don't obscure the code by introducing a lot of conditional compilation or similar. If you have any specific ideas, I recommend discussing them here or in separate issues before preparing a full PR (although a small prototype to demonstrate the idea might be useful).

[vitaut]

I'm closing this for now, but feel free to reopen or open another issue to discuss any specific suggestion in more details.