On 09/08/2016 08:19 PM, Martin Sebor wrote:
While working on the -Wformat-length pass I noticed that in some
diagnostics that make use of the %qc and %qs directives GCC prints
non-printable characters raw. For example, it might print a newline,
corrupting the diagnostic stream (bug 77521).
Some other diagnostics that try to avoid this problem by using
a directive such as %x when the character is not printable might
use the sign-extended value of the character, printing a very
large hexadecimal value (bug 77520).
The attached patch changes the pretty printer to detect non-printable
characters in %qc and %qs directives (but not %c or %s) and print
those in hexadecimal (via "\\x%02x").
Martin
PS I used hexadecimal based on what c-format.c does but now that
I checked more carefully how %qE formats string literals I see it
uses octal. I think hexadecimal is preferable because it avoids
ambiguity but I'm open to changing it to octal if there's a strong
preference for it. Incidentally, %qE too suffers from bug 77520
(see below). The patch doesn't try to fix that.
$ cat z.C && gcc z.C
constexpr int i = "ABC\x7f_\x80XYZ";
z.C:1:19: error: invalid conversion from ‘const char*’ to ‘int’
[-fpermissive]
constexpr int i = "ABC\x7f_\x80XYZ";
^~~~~~~~~~~~~~~~~
z.C:1:19: error: ‘(int)((const char*)"ABC\177_\37777777600XYZ")’ is not
a constant expression
gcc-77520.diff
PR c/77520 - wrong value for extended ASCII characters in -Wformat message
PR c/77521 - %qc format directive should quote non-printable characters
gcc/c-family/ChangeLog:
2016-09-08 Martin Sebor <mse...@redhat.com>
PR c/77520
PR c/77521
* c-format.c (argument_parser::find_format_char_info): Use %qc
format directive unconditionally.
gcc/ChangeLog:
2016-09-08 Martin Sebor <mse...@redhat.com>
PR c/77520
PR c/77521
* pretty-print.c (pp_quoted_string): New function.
(pp_format): Call it for %c and %s directives.
gcc/testsuite/ChangeLog:
2016-09-08 Martin Sebor <mse...@redhat.com>
PR c/77520
PR c/77521
* gcc.dg/pr77520.c: New test.
* gcc.dg/pr77521.c: New test.
I was about to ack, the realized Joseph already did and you'd already
installed the change :-)
Jeff
