# C Usage

## Usage Instructions for C

See the release bundle for some examples of C programs which can be compiled and run on Valida. Here is an example C program from this repo, called `cat.c`:

```
#include <stdio.h>

const unsigned EOF_ = 0xFFFFFFFF;

int main() {
    unsigned c = 0;
    while (1) {
        c = getchar();
        if (c == EOF_) {
            break;
        } else {
            putchar(c);
        }
    }
}
```

To compile the `cat.c` example to Valida from within the Valida shell or the Valida Docker image shell:

```bash
clang -target valida /valida-toolchain/example/c/cat.c -o cat
valida run cat log
```

Once running, the `cat` example will wait for input. After you are done providing input, press `ctrl+D`. The program should echo back what you wrote, writing its output to `log`.

Compiling and running the other examples follows the same procedure, substituting `$NAME` for the name of the example:

```bash
clang -target valida /valida-toolchain/examples/c/${NAME}.c -o ${NAME}
valida run ${NAME} log
```

### C standard libraries

See [Using LLVM libc](broken://pages/Rp0KOncdE4z5cwO0AoLX) for instructions on how to use the libc support included with the Valida toolchain. This allows for the use of some libc header files and standard library functions and macros.

### Floating point support

The LLVM Valida compiler toolchain supports floating point types via software emulation. All of the normal arithmetic operations on floating point are supported. `fenv.h` is not supported. It is recommended to avoid using floating point types in Valida, because it's not very efficient to do it using software emulation.


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