As of r247522, fix-it-hints can suggest the insertion of new lines.
This patch updates -Wimplicit-fallthrough to provide suggestions
with fix-it hints, showing the user where to insert "break;" or
fallthrough attributes.
For example:
test.c: In function 'set_x':
test.c:15:9: warning: this statement may fall through [-Wimplicit-fallthrough=]
x = a;
~~^~~
test.c:22:5: note: here
case 'b':
^~~~
test.c:22:5: note: insert '__attribute__ ((fallthrough));' to silence this
warning
+ __attribute__ ((fallthrough));
case 'b':
^~~~
test.c:22:5: note: insert 'break;' to avoid fall-through
+ break;
case 'b':
^~~~
The idea is that if an IDE supports -fdiagnostics-parseable-fixits, the
user can fix these issues by clicking on them.
It's loosely based on part of Marek's patch:
https://gcc.gnu.org/ml/gcc-patches/2016-08/msg01948.html
but with extra logic for locating a suitable place to insert the
fix-it hint, so that, if possible, it is on a line by itself before
the "case", indented the same as the prior statement. If that's not
possible, no fix-it hint is emitted.
In Marek's patch he wrote:
/* For C++17, we'd recommend [[fallthrough]];, but we're not
there yet. For C++11, recommend [[gnu::fallthrough]];. */
"[[fallthrough]]" appears to work, but it appears that lang_hooks.name
doesn't expose C++17 yet, so the patch recommends [[gnu::fallthrough]
for C++17.
Successfully bootstrapped®rtested on x86_64-pc-linux-gnu.
OK for trunk?
gcc/ChangeLog:
PR c/7652
* diagnostic.c (diagnostic_report_diagnostic): Only add fixits
to the edit_context if they can be auto-applied.
* gimplify.c (add_newline_fixit_with_indentation): New function.
(warn_implicit_fallthrough_r): Add suggestions on how to fix
-Wimplicit-fallthrough.
gcc/testsuite/ChangeLog:
PR c/7652
* g++.dg/Wimplicit-fallthrough-fixit-c++11.C: New test case.
* g++.dg/Wimplicit-fallthrough-fixit-c++98.C: New test case.
* gcc.dg/Wimplicit-fallthrough-fixit.c: New test case.
libcpp/ChangeLog:
PR c/7652
* include/line-map.h
(rich_location::fixits_cannot_be_auto_applied): New method.
(rich_location::fixits_can_be_auto_applied_p): New accessor.
(rich_location::m_fixits_cannot_be_auto_applied): New field.
* line-map.c (rich_location::rich_location): Initialize new field.
---
gcc/diagnostic.c | 3 +-
gcc/gimplify.c | 90 +++++++++++++++++++++-
.../g++.dg/Wimplicit-fallthrough-fixit-c++11.C | 43 +++++++++++
.../g++.dg/Wimplicit-fallthrough-fixit-c++98.C | 43 +++++++++++
gcc/testsuite/gcc.dg/Wimplicit-fallthrough-fixit.c | 73 ++++++++++++++++++
libcpp/include/line-map.h | 22 ++++++
libcpp/line-map.c | 3 +-
7 files changed, 274 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/Wimplicit-fallthrough-fixit-c++11.C
create mode 100644 gcc/testsuite/g++.dg/Wimplicit-fallthrough-fixit-c++98.C
create mode 100644 gcc/testsuite/gcc.dg/Wimplicit-fallthrough-fixit.c
diff --git a/gcc/diagnostic.c b/gcc/diagnostic.c
index dc81755..40509f1 100644
--- a/gcc/diagnostic.c
+++ b/gcc/diagnostic.c
@@ -942,7 +942,8 @@ diagnostic_report_diagnostic (diagnostic_context *context,
diagnostic->x_data = NULL;
if (context->edit_context_ptr)
- context->edit_context_ptr->add_fixits (diagnostic->richloc);
+ if (diagnostic->richloc->fixits_can_be_auto_applied_p ())
+ context->edit_context_ptr->add_fixits (diagnostic->richloc);
context->lock--;
diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index fd27eb1..19dd6dc 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -2038,6 +2038,60 @@ should_warn_for_implicit_fallthrough
(gimple_stmt_iterator *gsi_p, tree label)
return true;
}
+/* Attempt to add a fix-it hint to RICHLOC, suggesting the insertion
+ of a new line containing LINE_CONTENT (which does not need
+ a '\n' character).
+ The new line is to be inserted immediately before the
+ line containing NEXT, using the location of PREV to determine
+ indentation.
+ The new line will only be inserted if there is nothing on
+ NEXT's line before NEXT, and we can determine the indentation
+ of PREV. */
+
+static void
+add_newline_fixit_with_indentation (rich_location *richloc,
+ location_t prev,
+ location_t next,
+ const char *line_content)
+{
+ /* Check that the line containing NEXT is blank, up to NEXT. */
+ int line_width;
+ expanded_location exploc_next = expand_location (next);
+ const char *line
+ = location_get_source_line (exploc_next.file, exploc_next.line,
+ &line_width);
+ if (!line)
+ return;
+ if (line_width < exploc_next.column)
+ return;
+ /* Columns are 1-based. */
+ for (int column = 1; column < exploc_next.column; ++column)
+ if (!ISSPACE (line[column - 1]))
+ return;
+
+ /* Locate the start of the line containing NEXT. */
+ const line_map *map = linemap_lookup (line_table, next);
+ if (linemap_macro_expansion_map_p (map))
+ return;
+ const line_map_ordinary *ordmap = linemap_check_ordinary (map);
+ location_t start_of_line
+ = linemap_position_for_line_and_column (line_table, ordmap,
+ exploc_next.line, 1);
+
+ /* Generate an insertion string, indenting by the amount PREV
+ was indented. */
+ int prev_column = LOCATION_COLUMN (prev);
+ pretty_printer tmp_pp;
+ pretty_printer *pp = &tmp_pp;
+ /* Columns are 1-based. */
+ for (int column = 1; column < prev_column; ++column)
+ pp_space (pp);
+ pp_string (pp, line_content);
+ pp_newline (pp);
+
+ richloc->add_fixit_insert_before (start_of_line, pp_formatted_text (pp));
+}
+
/* Callback for walk_gimple_seq. */
static tree
@@ -2111,7 +2165,41 @@ warn_implicit_fallthrough_r (gimple_stmt_iterator
*gsi_p, bool *handled_ops_p,
OPT_Wimplicit_fallthrough_,
"this statement may fall through");
if (warned_p)
- inform (gimple_location (next), "here");
+ {
+ inform (gimple_location (next), "here");
+
+ /* Suggestion one: add attribute fallthrough. */
+ rich_location rloc_attr (line_table, gimple_location (next));
+ const char *attr_hint;
+ /* For C++17, we'd recommend [[fallthrough]];, but we're not
+ there yet. For C++11, recommend [[gnu::fallthrough]];. */
+ if (strncmp (lang_hooks.name, "GNU C++14", 9) == 0
+ || strncmp (lang_hooks.name, "GNU C++11", 9) == 0)
+ attr_hint = "[[gnu::fallthrough]];";
+ else
+ /* Otherwise, recommend __attribute__ ((fallthrough));. */
+ attr_hint = "__attribute__ ((fallthrough));";
+
+ add_newline_fixit_with_indentation (&rloc_attr,
+ gimple_location (prev),
+ gimple_location (next),
+ attr_hint);
+ rloc_attr.fixits_cannot_be_auto_applied ();
+ inform_at_rich_loc (&rloc_attr,
+ "insert %qs to silence this warning",
+ attr_hint);
+
+ /* Suggestion two: add "break;". */
+ rich_location rloc_break (line_table, gimple_location (next));
+ add_newline_fixit_with_indentation (&rloc_break,
+ gimple_location (prev),
+ gimple_location (next),
+ "break;");
+ rloc_break.fixits_cannot_be_auto_applied ();
+ inform_at_rich_loc (&rloc_break,
+ "insert %qs to avoid fall-through",
+ "break;");
+ }
/* Mark this label as processed so as to prevent multiple
warnings in nested switches. */
diff --git a/gcc/testsuite/g++.dg/Wimplicit-fallthrough-fixit-c++11.C
b/gcc/testsuite/g++.dg/Wimplicit-fallthrough-fixit-c++11.C
new file mode 100644
index 0000000..afc808e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/Wimplicit-fallthrough-fixit-c++11.C
@@ -0,0 +1,43 @@
+/* PR c/7652 */
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough -std=c++11 -fdiagnostics-show-caret
-fdiagnostics-generate-patch" } */
+/* We specify -fdiagnostics-generate-patch, but no patch should be
+ generated, since user-intervention is required to choose between
+ two different fix-it hints. */
+
+int x;
+
+void set_x (char ch, int a, int b)
+{
+ switch (ch)
+ {
+ case 'a':
+ x = a; /* { dg-warning "statement may fall through" } */
+ /* { dg-begin-multiline-output "" }
+ x = a;
+ ~~^~~
+ { dg-end-multiline-output "" } */
+
+ case 'b': /* { dg-line second_case } */
+ x = b;
+ /* { dg-message "here" "" { target *-*-* } second_case } */
+ /* { dg-begin-multiline-output "" }
+ case 'b':
+ ^~~~
+ { dg-end-multiline-output "" } */
+
+ /* { dg-message "insert '..gnu::fallthrough..;' to silence this warning"
"" { target *-*-* } second_case } */
+ /* { dg-begin-multiline-output "" }
++ [[gnu::fallthrough]];
+ case 'b':
+ ^~~~
+ { dg-end-multiline-output "" } */
+
+ /* { dg-message "insert 'break;' to avoid fall-through" "" { target
*-*-* } second_case } */
+ /* { dg-begin-multiline-output "" }
++ break;
+ case 'b':
+ ^~~~
+ { dg-end-multiline-output "" } */
+ }
+}
diff --git a/gcc/testsuite/g++.dg/Wimplicit-fallthrough-fixit-c++98.C
b/gcc/testsuite/g++.dg/Wimplicit-fallthrough-fixit-c++98.C
new file mode 100644
index 0000000..8730b4c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/Wimplicit-fallthrough-fixit-c++98.C
@@ -0,0 +1,43 @@
+/* PR c/7652 */
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough -std=c++98 -fdiagnostics-show-caret
-fdiagnostics-generate-patch" } */
+/* We specify -fdiagnostics-generate-patch, but no patch should be
+ generated, since user-intervention is required to choose between
+ two different fix-it hints. */
+
+int x;
+
+void set_x (char ch, int a, int b)
+{
+ switch (ch)
+ {
+ case 'a':
+ x = a; /* { dg-warning "statement may fall through" } */
+ /* { dg-begin-multiline-output "" }
+ x = a;
+ ~~^~~
+ { dg-end-multiline-output "" } */
+
+ case 'b': /* { dg-line second_case } */
+ x = b;
+ /* { dg-message "here" "" { target *-*-* } second_case } */
+ /* { dg-begin-multiline-output "" }
+ case 'b':
+ ^~~~
+ { dg-end-multiline-output "" } */
+
+ /* { dg-message "insert '__attribute__ \\(\\(fallthrough\\)\\);' to
silence this warning" "" { target *-*-* } second_case } */
+ /* { dg-begin-multiline-output "" }
++ __attribute__ ((fallthrough));
+ case 'b':
+ ^~~~
+ { dg-end-multiline-output "" } */
+
+ /* { dg-message "insert 'break;' to avoid fall-through" "" { target
*-*-* } second_case } */
+ /* { dg-begin-multiline-output "" }
++ break;
+ case 'b':
+ ^~~~
+ { dg-end-multiline-output "" } */
+ }
+}
diff --git a/gcc/testsuite/gcc.dg/Wimplicit-fallthrough-fixit.c
b/gcc/testsuite/gcc.dg/Wimplicit-fallthrough-fixit.c
new file mode 100644
index 0000000..53daca6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wimplicit-fallthrough-fixit.c
@@ -0,0 +1,73 @@
+/* PR c/7652 */
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough -fdiagnostics-show-caret
-fdiagnostics-generate-patch" } */
+/* We specify -fdiagnostics-generate-patch, but no patch should be
+ generated, since user-intervention is required to choose between
+ two different fix-it hints. */
+
+int x;
+
+void set_x (char ch, int a, int b)
+{
+ switch (ch)
+ {
+ case 'a':
+ x = a; /* { dg-warning "statement may fall through" } */
+ /* { dg-begin-multiline-output "" }
+ x = a;
+ ~~^~~
+ { dg-end-multiline-output "" } */
+
+
+ case 'b': /* { dg-line second_case } */
+ x = b;
+ /* { dg-message "here" "" { target *-*-* } second_case } */
+ /* { dg-begin-multiline-output "" }
+ case 'b':
+ ^~~~
+ { dg-end-multiline-output "" } */
+
+ /* { dg-message "insert '__attribute__ \\(\\(fallthrough\\)\\);' to
silence this warning" "" { target *-*-* } second_case } */
+ /* { dg-begin-multiline-output "" }
++ __attribute__ ((fallthrough));
+ case 'b':
+ ^~~~
+ { dg-end-multiline-output "" } */
+
+ /* { dg-message "insert 'break;' to avoid fall-through" "" { target
*-*-* } second_case } */
+ /* { dg-begin-multiline-output "" }
++ break;
+ case 'b':
+ ^~~~
+ { dg-end-multiline-output "" } */
+ }
+}
+
+#define FOO
+
+void set_x_2 (char ch, int a, int b)
+{
+ switch (ch)
+ {
+ case 'a':
+ x = a; /* { dg-warning "statement may fall through" } */
+ /* { dg-begin-multiline-output "" }
+ x = a;
+ ~~^~~
+ { dg-end-multiline-output "" } */
+
+FOO case 'b': /* { dg-line case_2 } */
+ x = b;
+ /* { dg-message "here" "" { target *-*-* } case_2 } */
+ /* { dg-begin-multiline-output "" }
+ FOO case 'b':
+ ^~~~
+ { dg-end-multiline-output "" } */
+
+ /* This case isn't the first thing on its line, so the suggestions
+ should not provide fix-it hints. */
+
+ /* { dg-message "insert '__attribute__ \\(\\(fallthrough\\)\\);' to
silence this warning" "" { target *-*-* } case_2 } */
+ /* { dg-message "insert 'break;' to avoid fall-through" "" { target
*-*-* } case_2 } */
+ }
+}
diff --git a/libcpp/include/line-map.h b/libcpp/include/line-map.h
index 90d65d7..be3041d 100644
--- a/libcpp/include/line-map.h
+++ b/libcpp/include/line-map.h
@@ -1663,6 +1663,27 @@ class rich_location
fixit_hint *get_last_fixit_hint () const;
bool seen_impossible_fixit_p () const { return m_seen_impossible_fixit; }
+ /* Set this if the fix-it hints are not suitable to be
+ automatically applied.
+
+ For example, if you are suggesting more than one
+ mutually exclusive solution to a problem, then
+ it doesn't make sense to apply all of the solutions;
+ manual intervention is required.
+
+ If set, then the fix-it hints in the rich_location will
+ be printed, but will not be added to generated patches,
+ or affect the modified version of the file. */
+ void fixits_cannot_be_auto_applied ()
+ {
+ m_fixits_cannot_be_auto_applied = true;
+ }
+
+ bool fixits_can_be_auto_applied_p () const
+ {
+ return !m_fixits_cannot_be_auto_applied;
+ }
+
private:
bool reject_impossible_fixit (source_location where);
void stop_supporting_fixits ();
@@ -1686,6 +1707,7 @@ protected:
semi_embedded_vec <fixit_hint *, MAX_STATIC_FIXIT_HINTS> m_fixit_hints;
bool m_seen_impossible_fixit;
+ bool m_fixits_cannot_be_auto_applied;
};
/* A fix-it hint: a suggested insertion, replacement, or deletion of text.
diff --git a/libcpp/line-map.c b/libcpp/line-map.c
index c4b7cb2..5caaf6b 100644
--- a/libcpp/line-map.c
+++ b/libcpp/line-map.c
@@ -2012,7 +2012,8 @@ rich_location::rich_location (line_maps *set,
source_location loc) :
m_column_override (0),
m_have_expanded_location (false),
m_fixit_hints (),
- m_seen_impossible_fixit (false)
+ m_seen_impossible_fixit (false),
+ m_fixits_cannot_be_auto_applied (false)
{
add_range (loc, true);
}
--
1.8.5.3
