Derive C

Elevator Pitch

When using C for complex projects, the lack of generics is frustrating:

• tradeoff performance and store runtime type information (e.g. size of items in a vector)
• tradeoff usability and restrict sizes of types, use unions (e.g. vector of only 8 byte items, user must cast to their own type, debuggers unaware of real type)
• tradeoff readability & development speed by outsourcing data structure generation to another language (cmake calling python to generate headers)
• tradeoff tooling for formatting, linting & intellisense with complex preprocessor macros to generate data structures

Derive-C aims to avoid these, and to get an experience close to simple templates in C++:

• templates are edittable (with intellisense), lintable, formattable independent of their usage.
• instances of templates should be clangd friendly / show types & completions
• no performance tradeoff
• easy to debug with in GDB

For example:

Create a vector of characters '1'-'9', iterate and print them. No heap allocation & no memory leaks.

#include <stdio.h>

#define CAPACITY 2048
#define NAME alloc_2048
#include <derive-c/allocs/staticbump/template.h>

#define ITEM char
#define ALLOC alloc_2048
#define NAME vec_char
#include <derive-c/structures/vector/template.h>

int main() {
    alloc_2048 alloc = alloc_2048_new();
    vec_char vec = vec_char_new(&alloc);

    for (char x = 1; x <= 9; x++) {
        vec_char_push(&vec, (char)('0' + x));
    }

    vec_char_iter_const iter = vec_char_get_iter_const(&vec);
    char const* entry;
    while ((entry = vec_char_iter_const_next(&iter))) {
        printf("entry: %c\n", *entry);
    }

    vec_char_delete(&vec);
}

• See more usage examples in ./examples

Use

In a CMakeLists.txt

include(FetchContent)

FetchContent_Declare(
    derive-c
    GIT_REPOSITORY https://github.com/OliverKillane/derive-C
    GIT_TAG <Chosen derive-c version>
)
FetchContent_MakeAvailable(derive-c)

Develop

nix-shell is included to setup the C/C++ toolchain.

nix-shell # from repo root

cmake -S . -B build -GNinja

cd build
ninja
ctest -j
ninja format
ninja lint
ninja docs
ninja coverage

Then when opening vscode from the nix-shell, the correct clangd & library paths are used:

code .

For using infer, infer must be installed separately (it is not yet packaged with nix - see here)

• Build with clang

cmake -S . -B build -DEXTERNALS=Off
infer run --compilation-database build/compile_commands.json --bufferoverrun --liveness --pulse
infer explore

• Statically detects generic bugs (e.g. use after free, buffer overrun, integer overflow)

TODO

In development, remaining tasks:

• Fix remaining infer-detected casting issues
• Finish gdb pretty printers
• Increase coverage for hashmap
• Regression benchmarks
• compare & optimise hashmap versus: ankerl

References

• moving-fast-with-software-verification