Re: [PATCH] correct handling of non-constant width and precision (pr 78521)

[Jeff Law <law@redhat.com>]

On 11/27/2016 08:34 PM, Martin Sebor wrote:
> PR 78521 notes that the gimple-ssa-sprintf pass doesn't do the right
> thing (i.e., the -Wformat-length and -fprintf-return-value options
> behave incorrectly) when a conversion specification includes a width
> or precision with a non-constant value.  The code treats such cases
> as if they were not provided which is incorrect and results in
> the wrong bytes counts in warning messages and in the wrong ranges
> being generated for such calls (or in the case sprintf(0, 0, ...)
> for some such calls being eliminated).
>
> The attached patch corrects the handling of these cases, plus a couple
> of other edge cases in the same area: it adjusts the parser to accept
> precision in the form of just a period with no asterisk or decimal
> digits after it (this sets the precision to zero), and corrects the
> handling of zero precision and zero argument in integer directives
> to produce no bytes on output.
>
> Finally, the patch also tightens up the constraint on the upper bound
> of bounded functions like snprintf to be INT_MAX.  The functions cannot
> produce output in excess of INT_MAX + 1 bytes and some implementations
> (e.g., Solaris) fail with EINVAL when the bound is INT_MAX or more.
> This is the subject of PR 78520.
>
> Thanks
> Martin
>
> gcc-78521.diff
>
>
> PR middle-end/78521 - [7 Regression] incorrect byte count in -Wformat-length warning with non-constant width or precision
> PR middle-end/78520 - missing warning for snprintf with size greater than INT_MAX
> gcc/ChangeLog:
>
> 	PR middle-end/78521
> 	PR middle-end/78520
> 	* gimple-ssa-sprintf.c (target_max_value): Remove.
> 	(target_int_max, target_size_max): Use TYPE_MAX_VALUE.
> 	(get_width_and_precision): New function.
> 	(format_integer, format_floating, get_string_length, format_string):
> 	Correct handling of width and precision with unknown value.
> 	(format_directive): Add warning.
> 	(pass_sprintf_length::compute_format_length): Allow for precision
> 	to consist of a sole period with no asterisk or digits after it.
>
> gcc/testsuite/ChangeLog:
>
> 	PR middle-end/78521
> 	PR middle-end/78520
> 	* gcc.dg/tree-ssa/builtin-sprintf-5.c: Add test cases.
> 	* gcc.dg/tree-ssa/builtin-sprintf-6.c: New test.
> 	* gcc.dg/tree-ssa/builtin-sprintf-warn-1.c: Add test cases.
> 	* gcc.dg/tree-ssa/builtin-sprintf-warn-3.c: Add test cases.
Fairly dense reading.  Probably inherent due to the problem space.

OK for the trunk.

Thanks,
jeff