INDENT

Indentation Style

This page describes the indentation style for the DreamBBS project.

Overview

• C & shell code
  • Indent with 4 spaces
  • No tabs

Good: ``c { sth }

**Bad:**
- 2-space (Maple3)
```c
{
  sth
}

• Hard tab

{
[tab]sth
}

• • No trailing spaces

  • Use \n for line breaks

  • Both K&R and Allman style are allowed, but they should not be mixed within a file, especially within a function

Bad:

• Mix Allman style with K&R style

if (cond)
{
} else {
}

Line continuation

• The indentation size of continued lines should be 2, 4, or 6 spaces
• Argument lists and initializer-lists
  • The elements should be indented or be aligned with the start of the list
  • The end of list without elements in the same line should be indented less that the elements
• No wrapping at operators with higher grouping precedence without wrapping at operators with lower grouping precedence

Good:

if (sth_long > 42
    && sth_else_long)

if (sth_long
    > (42 && sth_else_long))

Bad:

if (sth_long
    > 42 && sth_else_long)

if (sth_long > (42
    && sth_else_long))

• No line breaks between unary, prefix, and suffix operators other than . and -> and their operand
• If needed, line breaks must come after suffix operators . and ->
• If needed, line breaks should come before the binary operators other than assignments and comma

Good:

if (sth_long
    && sth_else_long)

Bad:

if (sth_long &&
    sth_else_long)

• For the condition operator, if needed, line breaks should come before ? or both ? and :

Good:

cond ? sth : else_sth

cond
    ? sth : else_sth

cond
    ? sth
    : else_sth

Bad:

cond ? sth
    : else_sth

cond ?
    sth : else_sth

cond ?
    sth : else_sth

cond ?
    sth
    : else_sth

Worse:

cond
    ? sth :
    else_sth

Alignment

• 如果 code 附近的相似 code 已被對齊排版，這段 code 應該對齊排版
• 新的 code 不應該對齊排版，除非附近相似的 code 已被對齊排版

Condition lists

• if/for/while/switch 與 condition list 之間應有剛好一個 space
• 例外：用來對齊 else if 後的 condition list 時，if 後可以有 6 個 spaces

Good:

[if/for/while/switch] (sth)

if      (sth)
...
else if (sth)

goto label

• goto label 可半 indent (2 spaces)，也可不 indent
• goto label 可以以所在 block 或 function 為基準做 indent

Good:

int func(void)
{
    if (sth)
    {
sth:
    }
}

int func(void)
{
    if (sth)
    {
  sth:
    }
}

int func(void)
{
    if (sth)
    {
    sth:
    }
}

int func(void)
{
    if (sth)
    {
      sth:
    }
}

Bad:

int func(void)
{
    sth:
}

int func(void)
{
    if (sth)
    {
        sth:
    }
}

switch

• case label 可 indent，可半 indent (2 spaces)，也可不 indent；半個 indent 視為沒有 indent
• case label 內的 code 要 indent
• case label 要以 switch 為基準做 indent

Good:

switch (sth)
{
case sth:
    code
}

switch (sth)
{
  case sth:
    code
}

switch (sth)
{
    case sth:
        code
}

switch (sth)
{
case sth:
    if (sth)
    {
case sth:
        code
    }
}

Bad:

switch (sth)
{
case sth:
code
}

switch (sth)
{
  case sth:
        code
}

switch (sth)
{
    case sth:
    code
}

switch (sth)
{
case sth:
    if (sth)
    {
    case sth:
        code
    }
}

{ & }

• C code

  • 在 parameter list 及 condition list 後，與 { 之間要有空白字元
  • 在 identifier 後，與 { 之間要有剛好一個 space
  • 在 identifier 前，與 } 之間要有 spaces

• 如果 else/else if 和之前的 } 在同一行裡，else 後面的 { 也要在這一行裡

Good:

• K&R style

} else {

• K&R style (Stroustrup)

}
else {

• Allman style

}
else
{

Bad:

} else
{

• 在代表 code block 的 { 之後，以及 } 之前，要有空白字元

Good:

{
    code
}

{
}

• One-liner

{ code }

{ }

Bad:

{code}

{ code}

{code }

{}

( & )

• ( 後與對應的 ) 前的 space 的使用應該一致，要就不使用 space，要就使用剛好一個 space
• 例外：在字串中的 ( 後與對應的 ) 前，如果一端是全形字，而另一端是半形字，不論全形字的那端有沒有使用 space，半形字的那一端都可以使用一個 space

Good:

• ( sth )
• (sth)
• ( )
• ()
• (sth...漢)
• ( sth...漢 )
• (漢...sth)
• ( 漢...sth )
• In the strings
  • "( sth...漢)"
  • "(漢...sth )"

Bad:

• ( sth)
• (sth )
• (sth...漢 )
• ( 漢...sth)

,

• C code
  • 在 initializer-list 中，, 不能在被註解掉的 element list 之首，應從註解移出到前一個 element 後
• Code
  • , 前不能有額外的 spaces
  • , 後和 expression 之間要有至少一個 space
  • , 後不能有不用於對齊的額外 spaces
  • 扣除空白字元之後，, 不能在一行之首
  • 例外：特殊功能字串不必符合此規則

Good:

sth, sth

sth,
sth

macro(,,)

macro(sth,, sth)

int a[] = {sth, sth, /* sth */};

Bad:

sth,sth

sth , sth

macro(, ,)

macro(sth, , sth)

int a[] = {sth, sth /* , sth */};

;

• C & shell code
  • ; 前不應有 spaces，除非 ; 前是行內註解
  • ; 後，與 expression 之間，應有空白字元
  • 扣除空白字元之後，; 可以單獨成行
  • 例外：ANSI escape sequence 相關的註解與字串不必符合此規則

Good:

code; sth

code;
sth

for (;;)

for (sth;; sth)

Bad:

code;sth

code ; sth

for (; ;)

for (sth; ; sth)

for (s;t;h)

Preprocessor directives

• The indentation size should be 1 or 2 spaces
• The indentation should be consistent within the whole block
• The indentation can come before or after #
• The indentation can be omitted only for short blocks

Good:

#if COND
#define STH sth
#endif

#if COND
  #define STH sth
#endif

#if COND
#  define STH sth
#endif

Bad:

#if COND
... [Large directive block without indentation]
#endif

• The indentation should be independent of the indentation of C code

Good:

#if sth
int func(void)
{
    if (sth)
    {
  #if sth_else
        code;
  #endif
    }
}
#endif

Bad:

#if sth
int func(void)
{
    if (sth)
    {
        #if sth_else
        code;
        #endif
    }
}
#endif

Related commands

find . -name "*.c" -execdir sh -c "indent -st -bap -bli0 -i4 -l79 -ncs -npcs -npsl -fca -lc79 -fc1 -ts4 {} > {}.new " \;
find . -name "*.c.new" -exec prename -f -v 's/\.new//' {} \;
find . -name "*.h" -execdir sh -c "indent -st -bap -bli0 -i4 -l79 -ncs -npcs -npsl -fca -lc79 -fc1 -ts4 {} > {}.new " \;
find . -name "*.h.new" -exec prename -f -v 's/\.new//' {} \;
find . -name "*.h" -exec sed -i 's/\t/    /g' {} \;
find . -name "*.c" -exec sed -i 's/\t/    /g' {} \;