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pgbackrest/CODING.md

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# pgBackRest <br/> Coding Standards
## Standards
### Indentation
Indentation is four spaces -- no tabs. Only file types that absolutely require tabs (e.g. `Makefile`) may use them.
### Naming
#### Variables
Variable names use camel case with the first letter lower-case.
- `stanzaName` - the name of the stanza
- `nameIdx` - loop variable for iterating through a list of names
Variable names should be descriptive. Avoid `i`, `j`, etc.
#### Types
Type names use camel case with the first letter upper case:
`typedef struct MemContext <...>`
`typedef enum {<...>} ErrorState;`
#### Constants
**#define Constants**
`#define` constants should be all caps with `_` separators.
```
#DEFINE MY_CONSTANT "STRING"
```
The value should be aligned at column 69 whenever possible.
This type of constant should mostly be used for strings. Use enums whenever possible for integer constants.
**Enum Constants**
Enum elements follow the same case rules as variables. They are strongly typed so this shouldn't present any confusion.
```
typedef enum
{
cipherModeEncrypt,
cipherModeDecrypt,
} CipherMode;
```
Note the comma after the last element. This reduces diff churn when new elements are added.
#### Macros
Macro names should be upper-case with underscores between words. Macros (except simple constants) should be avoided whenever possible as they make code less clear and test coverage harder to measure.
Macros should follow the format:
```
#define MACRO(paramName1, paramName2) \
<code>
```
If the macro defines a block it should look like:
```
#define MACRO_2(paramName1, paramName2) \
{ \
<code> \
}
```
Continuation characters should be aligned at column 132 (unlike the examples above that have been shortened for display purposes).
To avoid conflicts, variables in a macro will be named `[macro name]_[var name]`, e.g. `TEST_RESULT_resultExpected`. Variables that need to be accessed in wrapped code should be provided accessor macros.
#### Begin / End
Use `Begin` / `End` for names rather than `Start` / `Finish`, etc.
#### New / Free
Use `New` / `Free` for constructors and destructors rather than `Create` / `Destroy`, etc.
### Formatting
#### Braces
C allows braces to be excluded for a single statement. However, braces should be used when the control statement (if, while, etc.) spans more than one line or the statement to be executed spans more than one line.
No braces needed:
```
if (condition)
return value;
```
Braces needed:
```
if (conditionThatUsesEntireLine1 &&
conditionThatUsesEntireLine2)
{
return value;
}
```
```
if (condition)
{
return
valueThatUsesEntireLine1 &&
valueThatUsesEntireLine2;
}
```
## Language Elements
### Data Types
Don't get exotic - use the simplest type that will work.
Use `int` or `unsigned int` for general cases. `int` will be at least 32 bits. When not using `int` use one of the types defined in `common/type.h`.
### Macros
Don't use a macro when a function could be used instead. Macros make it hard to measure code coverage.
### Objects
Object-oriented programming is used extensively. The object pointer is always referred to as `this`.
## Testing
### Uncoverable/Uncovered Code
#### Uncoverable Code
The `uncoverable` keyword marks code that can never be covered. For instance, a function that never returns because it always throws a error. Uncoverable code should be rare to non-existent outside the common libraries and test code.
```
} // {uncoverable - function throws error so never returns}
```
Subsequent code that is uncoverable for the same reason is marked with `// {+uncoverable}`.
#### Uncovered Code
Marks code that is not tested for one reason or another. This should be kept to a minimum and an excuse given for each instance.
```
exit(EXIT_FAILURE); // {uncoverable - test harness does not support non-zero exit}
```
Subsequent code that is uncovered for the same reason is marked with `// {+uncovered}`.