C++

Guidlines for efficient C/C++ Code

Pass and return primitives as value to and from functions [Breymann] p177 ,[Davis]
Pass objects as const reference to functions and omit const only when the function is designed to modify the object [Breymann] p177
Return objects which are attributes of the class as const reference and objects wich are not class attributes (especially stack and heap objects) as value! [Breymann] p177
Prefer references to pointers. References (and reference types) are just syntactic sugar for pointers and do not cause runtime overhead [Breymann?], [Quiroz]
To avoid memory leaks encapsulate new and delete in the constructor and destructor of a class. Than create the instance of the class as automatic variable. [?]
Always declare constant primitives and objects with const
int is the most efficient type for local variables. (No filling with zero's necessary) [Davis]
Use stdint.h. It offers… [Davis]
- exact length types
- smallest types of at least given length and
- most efficient types
Larger data types as int are less efficient [Davis]
Use the size_t and ptdiff_t types for memory calculations, not the long type [Davis]
Unsigned types tend to be more efficient then signed [Davis]
Plain char is always the most efficient char type. For signed or unsigned char it depends on the target which one is more efficient. [Davis]
Declare global data and functions as static whenever possible but avoid static variables at function level whenever possible [Davis]
Use the restrict keyword for data that is modified by one certain pointer [Davis]
Declare variables in the innermost scope possible [Davis]
Prefer float types to double (Use 3.0f instead of 3.0 and sinf() instead of sin()) [Davis]
It most often more efficient to use the stack rather than the heap for variable length arrays. Expamle! [Davis]
Declare a function as inline when it is… [Davis]
- small
- called very often from few places (e.g. inside a loop)
Use a mutex for concurrent data access [Obiltschnig]
Do not use exceptions in realtime / embedded systems. They may have non-deterministic runtime behauviour. Use goto as alternative. [Obiltschnig], [Quiroz]
Use consts rather than preprocessor defines [Quiroz]
To avoid name collisions use namespaces rather than prefixes or classes [Quiroz]
Aviod Run-Time Type Identification (RTTI) at least for realtime / embedded systems [Quiroz]

References

[Breymann]	Ulrich Breymann. C++ Einführung und professionelle Programmierung
[Davis]	Greg Davis. Guidlines for efficient C/C++ Code. Lecture at the „Embedded Systems“ fair in Nuremberg 2009-03-04
[Obiltschnig]	Günter Obiltschnig. C++ for Safety-critical Systems. Lecture at the „Embedded Systems“ fair in Nuremberg 2009-03-04
[Quiroz]	César A Quiroz. Using C++ Efficiently In Embedded Applications. Mentor Graphics, Embedded Software Division

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Guidlines for efficient C/C++ Code

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