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Altera_Forum
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15 years ago

Gcc4 Frame Pointer Issue

I've been trying to write some code in an MPU exception handler to trap and dump the call stack when an intermittent exception occurs in our system and am pretty sure I've found a bug in the latest G...
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Altera_Forum
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12 years ago

To those who are interested in Alteras official statement:

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the GCC is not setting the frame pointer as documented in the ABI. Both the text and diagrams in the ABI document say the FP points at the saved FP on the stack. Instead, GCC is pointing it at the last saved register (i.e., at the low end of the frame), and consistently applying the wrong constant offset to all fp-based stack references. This bug was observed on the GCC 4.7.

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We have already filed this issue to Mentor (tracking number 16009) and the fixes is planned to be included in our Nios II GNU toolchain (upgrade to GCC4.8) in a future version of the Quartus II software.

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... So until this future becomes present, we do have to live with workarounds.