# How to C in 2016

## Declare variable in any block

Not

```
void test(uint8_t input) {
    uint32_t b;

    if (input > 3) {
        return;
    }

    b = input;
}
```

But

```
void test(uint8_t input) {
    if (input > 3) {
        return;
    }

    uint32_t b = input;
}
```

## For counter variable

Not

```
uint32_t i;

    for (i = 0; i < 10; i++)
```

But

```
for (uint32_t i = 0; i < 10; i++)
```

## Array initialization

Not

```
uint32_t numbers[64];
    memset(numbers, 0, sizeof(numbers));
```

But

```
uint32_t numbers[64] = {0};
```

## Structure initialization

Not

```
struct thing {
        uint64_t index;
        uint32_t counter;
    };

    struct thing localThing;

    void initThing(void) {
        memset(&localThing, 0, sizeof(localThing));
    }
```

But

```
struct thing {
        uint64_t index;
        uint32_t counter;
    };

    struct thing localThing = {0};
```

## Function input type

Not

```
void processAddBytesOverflow(uint8_t *bytes, uint32_t len) {
    for (uint32_t i = 0; i < len; i++) {
        bytes[0] += bytes[i];
    }
}
```

But

```
void processAddBytesOverflow(void *input, uint32_t len) {
    uint8_t *bytes = input;

    for (uint32_t i = 0; i < len; i++) {
        bytes[0] += bytes[i];
    }
}
```

將輸入型別設定為 void 並在內容中重新指派

## Return Type

若回傳值有「是」／「否」這種需求，建議引入 stdbool.h 函式庫，使用 true 或 false 來代替整數型態（例如 int32\_t）的 1 或 0。讓程式更容易閱讀。

可以的話，建議創一個 enum 來表示複合型態的回傳型別。例如：

```
typedef enum growthResult {
    GROWTH_RESULT_SUCCESS = 1, // 成功
    GROWTH_RESULT_FAILURE_GROW_NOT_NECESSARY, // 失敗 1
    GROWTH_RESULT_FAILURE_ALLOCATION_FAILED   // 失敗 2
} growthResult;
```

## Coding style

寫作習慣

程式沒人看得懂，功能再怎麼強都沒用。文章中建議使用自動格式工具（auto code formatter）：clang-format。

例如要對目標 main.c 進行轉換，在終端機中敲入：

```
$ clang-format -style="{BasedOnStyle: llvm, IndentWidth: 4, AllowShortFunctionsOnASingleLine: None, KeepEmptyLinesAtTheStartOfBlocks: false}" "$@" -i main.c
```

clang-format 會將將程式依建議重新排版。但是每次都這樣敲太麻煩了。可以將 clang-format 指令以 alias 的型式建在 .bash\_profie 或 .bash\_rc 中：

```
# .bash_profile or .bash_rc

alias clang-format='clang-format -style="{BasedOnStyle: llvm, IndentWidth: 4, AllowShortFunctionsOnASingleLine: None, KeepEmptyLinesAtTheStartOfBlocks: false}" "$@"'
```

之後就能直接以 clang-format 進行轉換：

```
$ clang-format -i main.c
```

其中若省略掉 -i 是直接在 bash 中預覽結果，而不將轉換結果覆寫掉目標檔案。

## Allocation

Not malloc bu calloc, and prevent memset


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