https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56856
--- Comment #11 from David Malcolm <dmalcolm at gcc dot gnu.org> --- Author: dmalcolm Date: Fri Oct 5 19:02:17 2018 New Revision: 264887 URL: https://gcc.gnu.org/viewcvs?rev=264887&root=gcc&view=rev Log: 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. Added: trunk/gcc/testsuite/g++.dg/warn/Wformat-method.C trunk/gcc/testsuite/g++.dg/warn/Wformat-pr71863.C trunk/gcc/testsuite/g++.dg/warn/Wformat-ranges-c++11.C trunk/gcc/testsuite/g++.dg/warn/Wformat-ranges.C Modified: trunk/gcc/ChangeLog trunk/gcc/cp/ChangeLog trunk/gcc/cp/call.c trunk/gcc/cp/cp-lang.c trunk/gcc/cp/parser.c trunk/gcc/input.c trunk/gcc/input.h trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/g++.dg/ext/builtin4.C trunk/gcc/testsuite/g++.dg/plugin/plugin.exp trunk/gcc/testsuite/gcc.dg/format/diagnostic-ranges.c trunk/gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-1.c trunk/gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-2.c
