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.