Support string locations for C++ in -Wformat (PR c++/56856)
authorDavid Malcolm <dmalcolm@redhat.com>
Fri, 5 Oct 2018 19:02:17 +0000 (19:02 +0000)
committerDavid Malcolm <dmalcolm@gcc.gnu.org>
Fri, 5 Oct 2018 19:02:17 +0000 (19:02 +0000)
commit0d48e8779c6a9ac88f5efd1b4a2d40f43ef75faf
tree153fa1d9d2a0ab481ba54a9f2f4ed6e311e2a5bf
parent1f58c814c0ade165b1691d79a79843ea31d6428b
Support string locations for C++ in -Wformat (PR c++/56856)

-Wformat in the C++ FE doesn't work as well as it could:
(a) it doesn't report precise locations within the string literal, and
(b) it doesn't underline arguments for those arguments !CAN_HAVE_LOCATION_P,
despite having location wrapper nodes.

For example:

  Wformat-ranges.C:32:10: warning: format '%s' expects argument of type 'char*', but argument 2 has type 'int' [-Wformat=]
  32 |   printf("hello %s", 42);
     |          ^~~~~~~~~~

(a) is due to not wiring up the langhook for extracting substring
    locations.

    This patch uses the one in c-family; it also fixes string literal
    parsing so that it records string concatenations (needed for
    extracting substring locations from concatenated strings).

(b) is due to the call to maybe_constant_value here:
       fargs[j] = maybe_constant_value (argarray[j]);
    within build_over_call.

    The patch fixes this by building a vec of location_t values when
    calling check_function_arguments.
    I attempted to eliminate the maybe_constant_value call here, but
    it's needed by e.g. check_function_sentinel for detecting NULL,
    and that code is in "c-family", so it can't simply call into
    maybe_constant_value (which is in "cp").

With this patch, the output for the above example is improved to:

  Wformat-ranges.C:32:18: warning: format '%s' expects argument of type 'char*', but argument 2 has type 'int' [-Wformat=]
  32 |   printf("hello %s", 42);
     |                 ~^   ~~
     |                  |   |
     |                  |   int
     |                  char*
     |                 %d

gcc/cp/ChangeLog:
PR c++/56856
* call.c (build_over_call): Build a vec of locations of the
arguments before the call to maybe_constant_value, and pass to
check_function_arguments.
* cp-lang.c (LANG_HOOKS_GET_SUBSTRING_LOCATION): Define as
c_get_substring_location.
* parser.c (cp_parser_string_literal): Capture string
concatenation locations.

gcc/ChangeLog:
PR c++/56856
* input.c (expand_location_to_spelling_point): Add param "aspect"
and use rather than hardcoding LOCATION_ASPECT_CARET.
(get_substring_ranges_for_loc): Handle the case of a single token
within a macro expansion.
* input.h (expand_location_to_spelling_point): Add "aspect" param,
defaulting to LOCATION_ASPECT_CARET.

gcc/testsuite/ChangeLog:
PR c++/56856
* g++.dg/ext/builtin4.C: Set expected location for warning to the
correct location within the format string.
* g++.dg/plugin/plugin.exp (plugin_test_list): Add the plugin and
files for testing locations within string literal locations from
the C frontend.
* g++.dg/warn/Wformat-method.C: New test.
* g++.dg/warn/Wformat-pr71863.C: New test.
* g++.dg/warn/Wformat-ranges-c++11.C: New test.
* g++.dg/warn/Wformat-ranges.C: New test, based on
gcc.dg/format/diagnostic-ranges.c.
* gcc.dg/plugin/diagnostic-test-string-literals-1.c
(test_multitoken_macro): Generalize expected output to work with
both C and C++.
* gcc.dg/plugin/diagnostic-test-string-literals-2.c
(test_stringified_token_1): Likewise.
(test_stringified_token_3): Likewise.

From-SVN: r264887
17 files changed:
gcc/ChangeLog
gcc/cp/ChangeLog
gcc/cp/call.c
gcc/cp/cp-lang.c
gcc/cp/parser.c
gcc/input.c
gcc/input.h
gcc/testsuite/ChangeLog
gcc/testsuite/g++.dg/ext/builtin4.C
gcc/testsuite/g++.dg/plugin/plugin.exp
gcc/testsuite/g++.dg/warn/Wformat-method.C [new file with mode: 0644]
gcc/testsuite/g++.dg/warn/Wformat-pr71863.C [new file with mode: 0644]
gcc/testsuite/g++.dg/warn/Wformat-ranges-c++11.C [new file with mode: 0644]
gcc/testsuite/g++.dg/warn/Wformat-ranges.C [new file with mode: 0644]
gcc/testsuite/gcc.dg/format/diagnostic-ranges.c
gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-1.c
gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-2.c