Re: [PATCH] Adding three new function attributes for static analysis of file descriptors

[David Malcolm <dmalcolm@redhat.com>]

On Fri, 2022-07-22 at 21:25 +0530, Immad Mir wrote:
> This patch adds three new function attributes to GCC that
> are used for static analysis of usage of file descriptors:
> 
> 1) __attribute__ ((fd_arg(N))): The attributes may be applied to a
> function that
> takes an open file descriptor at refrenced argument N.
> 
> It indicates that the passed filedescriptor must not have been
> closed.
> Therefore, when the analyzer is enabled with -fanalyzer, the
> analyzer may emit a -Wanalyzer-fd-use-after-close diagnostic
> if it detects a code path in which a function with this attribute is
> called with a closed file descriptor.
> 
> The attribute also indicates that the file descriptor must have been
> checked for
> validity before usage. Therefore, analyzer may emit
> -Wanalyzer-fd-use-without-check diagnostic if it detects a code path
> in
> which a function with this attribute is called with a file descriptor
> that has
> not been checked for validity.
> 
> 2) __attribute__((fd_arg_read(N))): The attribute is identical to
> fd_arg, but with the additional requirement that it might read from
> the file descriptor, and thus, the file descriptor must not have been
> opened
> as write-only.
> 
> The analyzer may emit a -Wanalyzer-access-mode-mismatch
> diagnostic if it detects a code path in which a function with this
> attribute is called on a file descriptor opened with O_WRONLY.
> 
> 3) __attribute__((fd_arg_write(N))): The attribute is identical to
> fd_arg_read
> except that the analyzer may emit a -Wanalyzer-access-mode-mismatch
> diagnostic if
> it detects a code path in which a function with this attribute is
> called on a
> file descriptor opened with O_RDONLY.

[...snip...]

Thanks for the updated patch.

This version looks good for trunk.  You indicated (in an off-list
email) that you've tested this, so please go ahead and push this.


Thanks
Dave