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Exception handling

Figure 32. Keil® Access to Show Caller Code in Contextual menu

6.3

Trapping div/0 exception

Most often, code execution causing a division by zero are difficult to investigate:

•

Nothing is neither triggered nor trapped.

•

Erroneous returned value generates an unexpected and unpredictable behavior that is

very difficult to analyze.

This chapter gives several tips in order to properly trap div/0 exceptions.

6.3.1

Cortex®-M0/M0+ case

For targets that do not support hardware division instructions (SDIV/UDIV), integer division-

by-zero errors can be trapped and identified by means of the appropriate C library helper

functions:

__aeabi_idiv0()

When integer division by zero is detected, a branch to __aeabi_idiv0() is made. A

breakpoint placed on __aeabi_idiv0() allow to trap the division by zero.

To ease the breakpoint application, override the default function:

void __aeabi_idiv0()

{

#ifdef DEBUG

__BKPT(0);

#endif

}

This way, and depending on IDE, the call stack or registers can be examined and the

offending line in the source code can be rapidly found.

To go further refer to section 7.7 of ARM® Compiler Software Development Guide.

SW4STM32C Datasheet(PDF) 51 Page - STMicroelectronics