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C++ style guide: Difference between revisions

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C++ style guide (edit)

Revision as of 02:18, 20 February 2024

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Add section for lambda expressions
(Add section for lambda expressions)
 
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</syntaxhighlight>
</syntaxhighlight>
==== #ifdef directives ====
Indent code that follows a conditional processor directive such as {{codeline|#ifdef}} or {{codeline|#else}}.
Example
<syntaxhighlight lang="cpp">
#if defined (HAVE_CONFIG_H)
#  include "config.h"
#endif
</syntaxhighlight>
The '#' character may also be placed with the directive rather than remaining in column 1 if this looks better.


==== Split long expressions ====
==== Split long expressions ====
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=== Namespace ===
=== Namespace ===


All code should be in the octave namespace. This is an ongoing project.  We
All code should be in the {{codeline|octave}} namespace or in a namespace below it.
are still moving existing classes into namespaces but all new classes
 
should go somewhere into the "octave" namespace.  There is 1 extra level for namespaces
Namespaces should start and stop using the special macros {{codeline|OCTAVE_BEGIN_NAMESPACE(XXX)}} and {{codeline|OCTAVE_END_NAMESPACE(XXX)}}.  There is no indentation of code that is placed into namespaces using these macros.
inside octave to be used with care, we don't want too many namespaces.
 
Ask before creating a new namespace.
Example
 
{{Code|Use of namespace macros|<syntaxhighlight lang="cpp">
OCTAVE_BEGIN_NAMESPACE(octave)


* Indent namespaces as any other block.  Emacs and other editors can do this automatically.
OCTAVE_BEGIN_NAMESPACE(math)
* Define namespace on the .cc files;
* Do not use "using X" directives;
* Do not declare anything on the std namespace;


{{Code|namespace style on a .h file|<syntaxhighlight lang="cpp">
template <typename T>
// Note indentation
void
namespace octave
umfpack_report_control (const double *Control);
{
 
  namespace math
OCTAVE_END_NAMESPACE(math)
  {
OCTAVE_END_NAMESPACE(octave)
    class foo
    {
    public:
      foo (...);
    };
  }
}
</syntaxhighlight>}}
</syntaxhighlight>}}


{{Code|namespace style on a .cc file|<syntaxhighlight lang="cpp">
If bare namespace directives must be used, as occasionally is required in Qt code, then the code within the namespace should be indented.
// Note indentation and that functions are not defined
 
// as "octave::math::foo:foo"
{{Code|bare namespace usage|<syntaxhighlight lang="cpp">
// Note indentation and that functions are not defined as "octave::math::foo:foo"
namespace octave
namespace octave
{
{
Line 195: Line 203:
}
}
</syntaxhighlight>}}
</syntaxhighlight>}}
==== Other Guidelines ====
* Do not use {{codeline|using XXX;}} directives
* Do not declare anything on the {{codeline|std::}} namespace


== Naming ==
== Naming ==
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</syntaxhighlight>
</syntaxhighlight>
|}
|}
=== new/delete ===
Pointers that will be allocated memory with {{codeline|new}} should be initialized with the C++ literal {{codeline|nullptr}}, not the numerical value 0 or the macro {{codeline|NULL}}.
The {{codeline|delete}} keyword accepts {{codeline|nullptr}} and programmers should not put an {{codeline|if (ptr)}} guard around {{codeline|delete}}.
{| class="wikitable"
! style="color:green;" | good
! style="color:darkred;" | bad
|-
| <syntaxhighlight lang="c++">
delete ptr;
</syntaxhighlight>
| <syntaxhighlight lang="c++">
if (ptr)
  delete ptr;
</syntaxhighlight>
|}
=== lambda expressions ===
When capturing variables from the surrounding function, explicitly list the variables being captured rather than relying on a default capture by value (`[=]`) or by reference (`[&]`).  This more clearly captures the programmer's intent and makes the code more understandable.


=== std::string ===
=== std::string ===
Rik
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