C51: When are Functions Re-Entrant?

Information in this article applies to:

• C51 All Versions

QUESTION

I know that functions which use just CPU registers are reentrant, when they call no other non-reentrant functions.

How can I be sure that a function uses just CPU registers?

Is this visible somewhere?

ANSWER

Yes, you may review the linker map file (extension *.M51 for BL51). Under the section OVERLAY MAP OF MODULE, all that have overlay able data segments are listed.

When your function is not listed, or when the function is listed, but no overlay segments are listed under the BIT or DATA GROUPS, the function uses just CPU registers.

It should be noted that the Linker/Locater checks during the overlay process of a non-reentrant function are called by more than one process. So when there is no warning message, you are almost safe there your program does not violate reentrancy.

MORE INFORMATION

• Refer to Reentrant Functions in the Cx51 User's Guide.
• Refer to Listing (MAP) File in the LX51 User's Guide.

SEE ALSO

• C51: Function Prototypes for Reentrant Functions
• C51: Functions That Are Reentrant
• C51: Using Non-reentrant Function in Main and Interrupts
• C51: Reentrant Functions and Variables

Last Reviewed: Thursday, February 25, 2021