cpu/avr*: Fix compilation with GCC 12.2.0 #18532
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A statement like `LKPR = (1 << CLKPCE);` which for the ATmega328P translates to `*((volatile uint8_t *)0x61) = (1 << 7);` is considered as accessing the first array element of a zero sized array by GCC 12.2.0. Assuming a zero size for memory not allocated by the compiler is quite insane, so we need to disable the diagnostics for the affected code. The most targeted approach would be using: ``` #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Warray-bounds" ... #pragma GCC diagnostic pop ``` But adding this around every memory mapped I/O access would render the code unreadable. Adding this around the `#include <avr/io.h>` instead would be ideal, but since e.g. `LKPR` is macro, the diagnostic would be still triggered when that macro is used in RIOT's C code. Instead, we add `-Wno-array-bounds` to the `CFLAGS`, but only for the low level AVR/ATmega/ATXmega code. As a result common code can still profit from the diagnostics, while code working with memory mapped I/O can still use the AVR libc.
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Closing in favor of #18533 |
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Contribution description
A statement like
LKPR = (1 << CLKPCE);which for the ATmega328P translates to*((volatile uint8_t *)0x61) = (1 << 7);is considered as accessing the first array element of a zero sized array by GCC 12.2.0. Assuming a zero size for memory not allocated by the compiler is quite insane, so we need to disable the diagnostics for the affected code. The most targeted approach would be using:But adding this around every memory mapped I/O access would render the code unreadable. Adding this around the
#include <avr/io.h>instead would be ideal, but since e.g.LKPRis macro, the diagnostic would be still triggered when that macro is used in RIOT's C code.Instead, we add
-Wno-array-boundsto theCFLAGS, but only for the low level AVR/ATmega/ATXmega code. As a result common code can still profit from the diagnostics, while code working with memory mapped I/O can still use the AVR libc.Finally, the common LED initialization code needed suppression of bogus
-Warray-boundswarnings.Testing procedure
Compilation should now work with AVR GCC version 12.2.0 and still work for older versions as before. The latter is checked by Murdock, the former check I can provide:
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masterUsing this PR
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