mainlining shenanigans
213d266ebf
When compiling with -Wformat, clang emits the following warning:
gpiolib-acpi.c:393:4: warning: format specifies type 'unsigned char' but the argument has type 'int' [-Wformat]
pin);
^~~
So warning that '%hhX' is paired with an 'int' is all just completely
mindless and wrong. Sadly, I can see a different bogus warning reason
why people would want to use '%02hhX'.
Again, the *sane* thing from a human perspective is to use '%02X. But
if the compiler doesn't do any range analysis at all, it could decide
that "Oh, that print format could need up to 8 bytes of space in the
result". Using '%02hhX' would cut that down to two.
And since we use
char ev_name[5];
and currently use "_%c%02hhX" as the format string, even a compiler
that doesn't notice that "pin <= 255" test that guards this all will
go "OK, that's at most 4 bytes and the final NUL termination, so it's
fine".
While a compiler - like gcc - that only sees that the original source
of the 'pin' value is a 'unsigned short' array, and then doesn't take
the "pin <= 255" into account, will warn like this:
gpiolib-acpi.c: In function 'acpi_gpiochip_request_interrupt':
gpiolib-acpi.c:206:24: warning: '%02X' directive writing between 2 and 4 bytes into a region of size 3 [-Wformat-overflow=]
sprintf(ev_name, "_%c%02X",
^~~~
gpiolib-acpi.c:206:20: note: directive argument in the range [0, 65535]
because gcc isn't being very good at that argument range analysis either.
In other words, the original use of 'hhx' was bogus to begin with, and
due to *another* compiler warning being bad, and we had that bad code
being written back in 2016 to work around _that_ compiler warning
(commit
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.