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[RFC]: zephyr: CMakeLists: disable packed-related warnings #8521

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[RFC]: zephyr: CMakeLists: disable packed-related warnings #8521

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2 changes: 2 additions & 0 deletions zephyr/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -830,6 +830,8 @@ if (NOT CONFIG_COMPILER_INLINE_FUNCTION_OPTION)
target_compile_options(SOF INTERFACE -fno-inline-functions)
endif()

target_compile_options(SOF INTERFACE -Wno-address-of-packed-member)
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@lgirdwood lgirdwood Nov 24, 2023 •
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Its better we keep this, what errors do you see, there may be other/better ways to resolve ? i.e. a snippet from the CC errors.

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It's mostly stuff like:

/zep_workspace/sof/src/include/sof/coherent.h: In function '__coherent_init_thread':
/zep_workspace/sof/src/include/sof/coherent.h:433:19: warning: taking address of packed member of 'struct coherent' may result in an unaligned pointer value [-Waddress-of-packed-member]
  433 |         list_init(&c->list);

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  1. no, no idea why struct coherent has to be packed, I'd say it doesn't. It was that way from day one of the coherent API
  2. we currently have only one used of the coherent API: src/lib/ams.c - is ams used at all, are there plans to use it? Does it really need and benefit from the coherent API? @kfrydryx
  3. removing that warning seems like not the right fix for this. I found this explanation on [1] why this warning is useful:

When a program accesses a misaligned member of a packed struct, the compiler generates whatever code is necessary to read or write the correct value.

If the address of a misaligned member is stored in a pointer object, dereferencing that pointer doesn't give the compiler an opportunity to generate that extra code.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51628


# SOF needs `typeof`, `__VA_ARGS__` and maybe other GNU C99
# extensions. TODO other flags required ?
target_compile_options(SOF INTERFACE $<$<COMPILE_LANGUAGE:C,ASM>: -std=gnu99>)
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