Understanding the stack and the heap are fundamental steps for all software developers. The importance of such understanding is inversely proportional to the amount of memory available on the platform, as both compete for a piece of the total memory space available on a system.
In some cases the developer has the choice of when to use one (either the stack or heap) more than the other. In other cases, a scenario may force the developer to work with minimal use of the stack, the heap, or both.
With this in mind, wolfSSL is introducing a new build option in CyaSSL. Developers can now choose a CyaSSL build that best matches their needs of using more stack and less heap OR more heap and less stack. This process is being accomplished by the refactoring of the CyaSSL code. Currently 90% of the encryption layer has been refactored to use the new option.
Small stack usage is not enabled by default. To enable it users must use the option “–enable-small-stack” when configuring the CyaSSL build as in the following example:
./configure –enable-small-stack [other options]
For users who don`t use CyaSSL`s configure script for compilation, smaller stack usage is not enabled by default. In this case, users will need to add the compiler directive CYASSL_SMALL_STACK in config.h file or settings.h to enjoy its benefits as in the following example:
#define CYASSL_SMALL_STACK
or
#define CYASSL_SMALL_STACK 1
If you have any questions about stack usage with CyaSSL please let us know at facts@wolfssl.com.