Reducing Static Storage

Reducing Static Storage

Static storage refers to the memory for global and local static variables, string constants and floating-point constants. All of the general size-reduction above can reduce the size of the global and static variables.

String literal static memory. The space requirements for string constants can be reduced if the compiler has an option to merge identical string constants (which arise quite frequently). If there is no such option, or the option does not merge string constants across object files (which is quite likely), merging string constants can be achieved by the programmer, although the method is far from elegant. For example, including this variable in a header file and using it in multiple files may create multiple copies of the string literal:

    #define TITLE "A very long string ... "

Instead, a global variable can be declared to hold the string constant and the name of this char array is used instead of the string constant. In modern C++ you can use “inline variables” to avoid linker problems with multiple definitions.

inline const char TITLE[] = "A very long string ... ";

This change is unlikely to reduce the speed of the program, nor does it increase memory requirements even if TITLE is used only once (there may seem to be an extra 4 bytes to hold a pointer value pointing at where the string of characters is stored, but this is not so).

Large global variables. If there is a large global or static variable or array, the amount of static storage can be reduced by allocating it on the heap using malloc or the new operator, or by making it an automatic variable. This is particularly useful if the object has a short “lifetime”, in the sense that it is used only briefly (e.g. the array is used as temporary storage inside a function). If the variable is used all the time, this change doesn’t reduce the overall space problem, but simply moves the problem to another area.

 

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