FAQ-0521 KERN-EXEC 3 When Passing C++ bool Parameters on MARM


FAQ-0521 KERN-EXEC 3 When Passing C++ bool Parameters on MARM

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Classification:	C++	Category:	Utilities & Build Tools
Created:	09/21/2000	Modified:	09/01/2001
Number:	FAQ-0521
Platform:	ER5

Question:
KERN-EXEC 3 When Passing C++ bool Parameters on MARM

Answer:
Passing a bool under MARM can cause problems due to a bug in the GCC ARM compiler that comes with the C++ SDK. GCC will pass the first 4 parameters to a function in registers (or less if they are more than 4 bytes in size), and the remainder will be placed on the stack. GCC stores a bool object in 1 byte, but makes a mistake when passing a bool as one of these stacked parameters - instead of decrementing the stack pointer by 4 it only decrements it by 1 when passing the bool.

That is basically guaranteed to cause an alignment fault a few instructions later when the stack pointer is used again - and that exception generates a KERN-EXEC 3 panic.

You can avoid this bug in GCC by passing the boolean value in any integral type instead of bool.