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Diffstat (limited to 'README.md')
| -rw-r--r-- | README.md | 59 |
1 files changed, 57 insertions, 2 deletions
@@ -23,9 +23,64 @@ x : int; x = 5; // Declare x as an integer, then set it to 5. `toc` is statically typed and has many of C's features, but it is nearly as fast in theory. - + See `docs` for more information (in progress). `tests` has some test programs written in `toc`. -To compile the compiler on a Unix-y system, use +To compile the compiler on a Unix-y system, just run `build.sh`. You can supply a compiler by running `CC=tcc build.sh`, or built it in release mode with `./build.sh release` (which will help speed up compiling large programs). + +On other systems, you can just compile main.c with a C compiler. toc uses several C99 and a couple of C11 features, so it might not work on all compilers. But it does compile on quite a few, including `clang`, `gcc`, and `tcc`. It can also be compiled as if it were C++, but it does break the standard in a few places\*. So, MSVC can also compile it. The *outputted* code should be C99-compliant. + +--- + +### `toc` Source Code + +`toc` is written in C, for speed and portability. It has no dependencies, other than the C runtime library. + +#### Build system +`toc` is set up as a unity build, meaning that there is only one translation unit. So, `main.c` `#include`s `toc.c`, which `#include`s all of `toc`'s files. This improves (from scratch) compilation speeds, since you don't have to include headers a bunch of times for each translation unit. This is more of a problem in C++, where, for example, doing `#include <map>` ends up turning into 25,000 lines after preprocessing. All of toc's source code, which includes most of the C standard library, at the time of this writing (Dec 2019) is only 22,000 lines after preprocessing; imagine including all of that once for each translation unit which includes `map`. It also obviates the need for fancy build systems like CMake. + +#### New features + +Here are all the C99 features which `toc` depends on (I might have forgotten some...): + +- Declare anywhere +- `stdint.h` +- Non-constant struct literal initializers (e.g. `int x[2] = {y, z};`) +- Variadic macros and `__VA_ARGS__` +- Flexible array members + +The last three of those could all be removed fairly easily. + +And here are all of its C11 features: + +- Anonymous structures/unions +- `max_align_t` and `alignof` - It can still compile without these but it won't technically be standard-compliant + +#### More + +See `main.c` for a bit more information. + +--- + + +\* for those curious, it has to do with `goto`. In C, this program: +<pre><code> +int main() { + goto label; + int x = 5; + label: + return 0; +} +</code></pre> +Is completely fine. `x` will hold an unspecified value after the jump (but it isn't used so it doesn't really matter). Apparently, in C++, this is an ill-formed program. This is a bit ridiculous since +<pre><code> +int main() { + goto label; + int x; x = 5; + label: + return 0; +} +</code></pre> +is fine. So that's an interesting little "fun fact": `int x = 5;` isn't always the same as `int x; x = 5;` in C++. |