[U-Boot] [RFC PATCH 1/2] Makefile: Use -fno-strict-aliasing globally

[Tom Rini]

On Mon, Sep 10, 2018 at 06:53:45AM -0700, Bin Meng wrote:

> The -fstrict-aliasing option is implicitly enabled at levels -O2,
> -O3, -Os by GCC. This option allows the compiler to assume the
> strictest aliasing rules applicable to the language being compiled.
> For example, the practice of reading from a different union member
> than the one most recently written to (called "type-punning") is
> common. In this case, "type-punning" only works if the memory is
> accessed through the union type, but might not work by taking the
> address, casting the resulting pointer and dereferencing the result,
> which is an undefined behavior per the "strict aliasing rules".
> 
> GCC's -Wstrict-aliasing (included in -Wall) option does not catch
> all cases, but does attempt to catch the more common pitfalls. So
> there are cases that GCC does not report but the codes are violating
> the "strict aliasing rules".
> 
> Given lots of codes that may be written to rely on "type-punning",
> and Linux kernel disables it by -fno-strict-aliasing globally, since
> U-Boot currently does this on nds32/riscv/x86 builds only, extend
> this for all architecture builds.
> 
> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>

Reviewed-by: Tom Rini <trini at konsulko.com>

-- 
Tom
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