Following on from the thread on the "gcc" list here:
https://gcc.gnu.org/ml/gcc/2018-04/msg00172.html
here's an updated version of Jonathan's patch, which:
* eliminates the separate "note" in favor of simplying having
the warning itself emit the "return *this;" fix-it hint
pr85523.C: In member function 's1& s1::operator=(const s1&)':
pr85523.C:7:30: warning: no return statement in function returning
non-void [-Wreturn-type]
s1& operator=(const s1&) { }
^
return *this;
In doing so I guarded it with a call to:
global_dc->option_enabled (OPT_Wreturn_type
as per the insides of diagnostic.s, since adding a fix-it hint to
a rich_location is non-trivial (e.g. it requires an allocation).
* uses the new gcc_rich_location::add_fixit_insert_formatted to
make the fix-it hint respect typical C++ code formatting
conventions
* adds testcases
Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
OK for trunk?
Note for ChangeLog: jwakely is co-author.
gcc/cp/ChangeLog:
PR c++/85523
* decl.c: Include "gcc-rich-location.h".
(add_return_star_this_fixit): New function.
(finish_function): When warning about missing return statements in
functions returning non-void, add a "return *this;" fix-it hint for
assignment operators.
gcc/testsuite/ChangeLog:
PR c++/85523
* g++.dg/pr85523.C: New test.
---
gcc/cp/decl.c | 34 +++++++++++++++-
gcc/testsuite/g++.dg/pr85523.C | 88 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 120 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/pr85523.C
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 07f3a61..7952106 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -51,6 +51,7 @@ along with GCC; see the file COPYING3. If not see
#include "builtins.h"
#include "gimplify.h"
#include "asan.h"
+#include "gcc-rich-location.h"
/* Possible cases of bad specifiers type used by bad_specifiers. */
enum bad_spec_place {
@@ -15677,6 +15678,22 @@ maybe_save_function_definition (tree fun)
register_constexpr_fundef (fun, DECL_SAVED_TREE (fun));
}
+/* Attempt to add a fix-it hint to RICHLOC suggesting the insertion
+ of "return *this;" immediately before its location, using FNDECL's
+ first statement (if any) to give the indentation, if appropriate. */
+
+static void
+add_return_star_this_fixit (gcc_rich_location *richloc, tree fndecl)
+{
+ location_t indent = UNKNOWN_LOCATION;
+ tree stmts = expr_first (DECL_SAVED_TREE (fndecl));
+ if (stmts)
+ indent = EXPR_LOCATION (stmts);
+ richloc->add_fixit_insert_formatted ("return *this;",
+ richloc->get_loc (),
+ indent);
+}
+
/* Finish up a function declaration and compile that function
all the way to assembler language output. The free the storage
for the function definition. INLINE_P is TRUE if we just
@@ -15870,8 +15887,21 @@ finish_function (bool inline_p)
&& !DECL_DESTRUCTOR_P (fndecl)
&& targetm.warn_func_return (fndecl))
{
- warning (OPT_Wreturn_type,
- "no return statement in function returning non-void");
+ gcc_rich_location richloc (input_location);
+ /* Potentially add a "return *this;" fix-it hint for
+ assignment operators. */
+ if (IDENTIFIER_ASSIGN_OP_P (DECL_NAME (fndecl)))
+ {
+ tree valtype = TREE_TYPE (DECL_RESULT (fndecl));
+ if (TREE_CODE (valtype) == REFERENCE_TYPE
+ && same_type_ignoring_top_level_qualifiers_p
+ (TREE_TYPE (valtype), TREE_TYPE (current_class_ref)))
+ if (global_dc->option_enabled (OPT_Wreturn_type,
+ global_dc->option_state))
+ add_return_star_this_fixit (&richloc, fndecl);
+ }
+ warning_at (&richloc, OPT_Wreturn_type,
+ "no return statement in function returning non-void");
TREE_NO_WARNING (fndecl) = 1;
}
diff --git a/gcc/testsuite/g++.dg/pr85523.C b/gcc/testsuite/g++.dg/pr85523.C
new file mode 100644
index 0000000..9cd939b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr85523.C
@@ -0,0 +1,88 @@
+/* { dg-options "-fdiagnostics-show-caret" } */
+
+/* Verify that we emit a "return *this;" fix-it hint for
+ a missing return in an assignment operator. */
+
+struct s1 {
+ s1& operator=(const s1&) { } // { dg-warning "no return statement in
function returning non-void" }
+ /* { dg-begin-multiline-output "" }
+ s1& operator=(const s1&) { }
+ ^
+ return *this;
+ { dg-end-multiline-output "" } */
+};
+
+/* Likewise for +=. */
+
+struct s2 {
+ s2& operator+=(const s2&) {} // { dg-warning "no return statement in
function returning non-void" }
+ /* { dg-begin-multiline-output "" }
+ s2& operator+=(const s2&) {}
+ ^
+ return *this;
+ { dg-end-multiline-output "" } */
+};
+
+/* No warning for "void" return. */
+
+struct s3 {
+ void operator=(const s3&) { }
+};
+
+/* We shouldn't issue the fix-it hint if the return type isn't right. */
+
+struct s4 {
+ int operator=(int) { } // { dg-warning "no return statement in function
returning non-void" }
+ /* { dg-begin-multiline-output "" }
+ int operator=(int) { }
+ ^
+ { dg-end-multiline-output "" } */
+};
+
+/* Example of a multi-line fix-it hint. */
+
+struct s5 {
+ int i;
+ s5& operator=(const s5& z) {
+ i = z.i;
+ } // { dg-warning "no return statement in function returning non-void" }
+ /* { dg-begin-multiline-output "" }
++ return *this;
+ }
+ ^
+ { dg-end-multiline-output "" } */
+};
+
+/* Example of a multi-line fix-it hint with other statements. */
+
+extern void log (const char *);
+struct s6 {
+ int i;
+ s6& operator=(const s6& z) {
+ log ("operator=\n");
+ i = z.i;
+ } // { dg-warning "no return statement in function returning non-void" }
+ /* { dg-begin-multiline-output "" }
++ return *this;
+ }
+ ^
+ { dg-end-multiline-output "" } */
+};
+
+/* Another example of a multi-line fix-it hint with other statements. */
+
+struct s7 {
+ int i;
+ s7& operator=(const s6& z) {
+ if (z.i)
+ log ("operator=\n");
+ else
+ log ("operator=\n");
+ i = z.i;
+ } // { dg-warning "no return statement in function returning non-void" }
+ /* { dg-begin-multiline-output "" }
++ return *this;
+ }
+ ^
+ { dg-end-multiline-output "" } */
+};
--
1.8.5.3
