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[google] Add two new -Wshadow warnings (issue4452058)
- From: dnovillo at google dot com (Diego Novillo)
- To: reply at codereview dot appspotmail dot com, lcwu at google dot com, jason at redhat dot com, joseph at codesourcery dot com, gcc-patches at gcc dot gnu dot org
- Date: Fri, 29 Apr 2011 10:55:46 -0400 (EDT)
- Subject: [google] Add two new -Wshadow warnings (issue4452058)
This patch from Le-Chun Wu adds two two new shadow warning flags for
C and C++:
-Wshadow-local which warns if a local variable shadows another local
variable or parameter,
-Wshadow-compatible-local which warns if a local variable shadows another
local variable or parameter whose type is compatible with that of the
shadowing variable.
OK for trunk? Applied to google/main
2011-04-27 Le-Chun Wu <lcwu@google.com>
Google ref 39127.
* c-decl.c (warn_if_shadowing): Use the warning code corresponding
to the given -Wshadow- variant.
* common.opt (Wshadow-local): New option.
(Wshadow-compatible-local): New option.
* invoke.texi: Document Wshadow-local and Wshadow-compatible-local.
* opts.c (common_handle_option): Handle OPT_Wshadow and
OPT_Wshadow_local.
Do not enable Wshadow-local nor Wshadow-compatible-local if
Wshadow is disabled.
cp/ChangeLog.google-main
2011-04-27 Le-Chun Wu <lcwu@google.com>
* name-lookup.c (pushdecl_maybe_friend): When emitting a
shadowing warning, use the code corresponding to the
given -Wshadow- variant.
testsuite/ChangeLog.google-main
2011-04-27 Le-Chun Wu <lcwu@google.com>
* g++.dg/warn/Wshadow-compatible-local-1.C: New.
* g++.dg/warn/Wshadow-local-1.C: New.
* g++.dg/warn/Wshadow-local-2.C: New.
* gcc.dg/Wshadow-compatible-local-1.c: New.
* gcc.dg/Wshadow-local-1.c: New.
* gcc.dg/Wshadow-local-2.c: New.
* gcc.dg/Wshadow-local-3.c: New.
diff --git a/gcc/c-decl.c b/gcc/c-decl.c
index 112e814..4a6a17d 100644
--- a/gcc/c-decl.c
+++ b/gcc/c-decl.c
@@ -2565,7 +2565,9 @@ warn_if_shadowing (tree new_decl)
struct c_binding *b;
/* Shadow warnings wanted? */
- if (!warn_shadow
+ if (!(warn_shadow
+ || warn_shadow_local
+ || warn_shadow_compatible_local)
/* No shadow warnings for internally generated vars. */
|| DECL_IS_BUILTIN (new_decl)
/* No shadow warnings for vars made for inlining. */
@@ -2579,30 +2581,55 @@ warn_if_shadowing (tree new_decl)
tree old_decl = b->decl;
if (old_decl == error_mark_node)
- {
- warning (OPT_Wshadow, "declaration of %q+D shadows previous "
- "non-variable", new_decl);
- break;
- }
+ warning (OPT_Wshadow, "declaration of %q+D shadows previous "
+ "non-variable", new_decl);
else if (TREE_CODE (old_decl) == PARM_DECL)
- warning (OPT_Wshadow, "declaration of %q+D shadows a parameter",
- new_decl);
+ {
+ enum opt_code warning_code;
+
+ /* If '-Wshadow-compatible-local' is specified without other
+ -Wshadow flags, we will warn only when the types of the
+ shadowing variable (i.e. new_decl) and the shadowed variable
+ (old_decl) are compatible. */
+ if (comptypes (TREE_TYPE (old_decl), TREE_TYPE (new_decl)))
+ warning_code = OPT_Wshadow_compatible_local;
+ else
+ warning_code = OPT_Wshadow_local;
+ warning (warning_code,
+ "declaration of %q+D shadows a parameter", new_decl);
+ warning_at (DECL_SOURCE_LOCATION (old_decl), warning_code,
+ "shadowed declaration is here");
+ }
else if (DECL_FILE_SCOPE_P (old_decl))
- warning (OPT_Wshadow, "declaration of %q+D shadows a global "
- "declaration", new_decl);
+ {
+ warning (OPT_Wshadow, "declaration of %q+D shadows a global "
+ "declaration", new_decl);
+ warning_at (DECL_SOURCE_LOCATION (old_decl), OPT_Wshadow,
+ "shadowed declaration is here");
+ }
else if (TREE_CODE (old_decl) == FUNCTION_DECL
&& DECL_BUILT_IN (old_decl))
- {
- warning (OPT_Wshadow, "declaration of %q+D shadows "
- "a built-in function", new_decl);
- break;
- }
+ warning (OPT_Wshadow, "declaration of %q+D shadows "
+ "a built-in function", new_decl);
else
- warning (OPT_Wshadow, "declaration of %q+D shadows a previous local",
- new_decl);
-
- warning_at (DECL_SOURCE_LOCATION (old_decl), OPT_Wshadow,
- "shadowed declaration is here");
+ {
+ enum opt_code warning_code;
+
+ /* If '-Wshadow-compatible-local' is specified without other
+ -Wshadow flags, we will warn only when the types of the
+ shadowing variable (i.e. new_decl) and the shadowed variable
+ (old_decl) are compatible. */
+ if (comptypes (TREE_TYPE (old_decl), TREE_TYPE (new_decl)))
+ warning_code = OPT_Wshadow_compatible_local;
+ else
+ warning_code = OPT_Wshadow_local;
+ warning (warning_code,
+ "declaration of %q+D shadows a previous local",
+ new_decl);
+
+ warning_at (DECL_SOURCE_LOCATION (old_decl), warning_code,
+ "shadowed declaration is here");
+ }
break;
}
diff --git a/gcc/common.opt b/gcc/common.opt
index 8ef5693..c0c7bd8 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -573,6 +573,15 @@ Wshadow
Common Var(warn_shadow) Warning
Warn when one local variable shadows another
+Wshadow-local
+Common Var(warn_shadow_local) Warning
+Warn when one local variable shadows another local variable or parameter
+
+Wshadow-compatible-local
+Common Var(warn_shadow_compatible_local) Warning
+Warn when one local variable shadows another local variable or parameter
+of compatible type
+
Wstack-protector
Common Var(warn_stack_protect) Warning
Warn when not issuing stack smashing protection for some reason
diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index 5d45e40..115437f 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -1080,22 +1080,44 @@ pushdecl_maybe_friend (tree x, bool is_friend)
}
}
- if (warn_shadow && !nowarn)
+ if ((warn_shadow
+ || warn_shadow_local
+ || warn_shadow_compatible_local)
+ && !nowarn)
{
+ enum opt_code warning_code;
+ /* If '-Wshadow-compatible-local' is specified without other
+ -Wshadow flags, we will warn only when the type of the
+ shadowing variable (i.e. x) can be converted to that of
+ the shadowed parameter (oldlocal). The reason why we only
+ check if x's type can be converted to oldlocal's type
+ (but not the other way around) is because when users
+ accidentally shadow a parameter, more than often they
+ would use the variable thinking (mistakenly) it's still
+ the parameter. It would be rare that users would use the
+ variable in the place that expects the parameter but
+ thinking it's a new decl. */
+ if (can_convert (TREE_TYPE (oldlocal), TREE_TYPE (x)))
+ warning_code = OPT_Wshadow_compatible_local;
+ else
+ warning_code = OPT_Wshadow_local;
if (TREE_CODE (oldlocal) == PARM_DECL)
- warning_at (input_location, OPT_Wshadow,
+ warning_at (input_location, warning_code,
"declaration of %q#D shadows a parameter", x);
else
- warning_at (input_location, OPT_Wshadow,
+ warning_at (input_location, warning_code,
"declaration of %qD shadows a previous local",
x);
- warning_at (DECL_SOURCE_LOCATION (oldlocal), OPT_Wshadow,
+ warning_at (DECL_SOURCE_LOCATION (oldlocal), warning_code,
"shadowed declaration is here");
}
}
/* Maybe warn if shadowing something else. */
- else if (warn_shadow && !DECL_EXTERNAL (x)
+ else if ((warn_shadow
+ || warn_shadow_local
+ || warn_shadow_compatible_local)
+ && !DECL_EXTERNAL (x)
/* No shadow warnings for internally generated vars unless
it's an implicit typedef (see create_implicit_typedef
in decl.c). */
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index cffc70d..fa247b6 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -259,6 +259,7 @@ Objective-C and Objective-C++ Dialects}.
-Wpointer-arith -Wno-pointer-to-int-cast @gol
-Wredundant-decls -Wreturn-type -Wripa-opt-mismatch @gol
-Wself-assign -Wself-assign-non-pod -Wsequence-point -Wshadow @gol
+-Wshadow-compatible-local -Wshadow-local @gol
-Wsign-compare -Wsign-conversion -Wstack-protector @gol
-Wstrict-aliasing -Wstrict-aliasing=n @gol
-Wstrict-overflow -Wstrict-overflow=@var{n} @gol
@@ -4052,6 +4053,43 @@ parameter, type, or class member (in C++), or whenever a built-in function
is shadowed. Note that in C++, the compiler will not warn if a local variable
shadows a struct/class/enum, but will warn if it shadows an explicit typedef.
+@item -Wshadow-local
+@opindex Wshadow-local
+@opindex Wno-shadow-local
+Warn when a local variable shadows another local variable or parameter.
+
+@item -Wshadow-compatible-local
+@opindex Wshadow-compatible-local
+@opindex Wno-shadow-compatible-local
+Warn when a local variable shadows another local variable or parameter
+whose type is compatible with that of the shadowing variable. In C++,
+type compatibility here means the type of the shadowing variable can be
+converted to that of the shadowed variable. The creation of this flag
+(in addition to @option{-Wshadow-local}) is based on the idea that when
+a local variable shadows another one of incompatible type, it is most
+likely intentional, not a bug or typo, as shown in the following example:
+
+@smallexample
+@group
+for (SomeIterator i = SomeObj.begin(); i != SomeObj.end(); ++i)
+@{
+ for (int i = 0; i < N; ++i)
+ @{
+ ...
+ @}
+ ...
+@}
+@end group
+@end smallexample
+
+Since the two variable @code{i} in the example above have incompatible types,
+enabling only @option{-Wshadow-compatible-local} will not emit a warning.
+Because their types are incompatible, if a programmer accidentally uses one
+in place of the other, type checking will catch that and emit an error or
+warning. So not warning (about shadowing) in this case will not lead to
+undetected bugs. Use of this flag instead of @option{-Wshadow-local} can
+possibly reduce the number of warnings triggered by intentional shadowing.
+
@item -Wlarger-than=@var{len}
@opindex Wlarger-than=@var{len}
@opindex Wlarger-than-@var{len}
diff --git a/gcc/opts.c b/gcc/opts.c
index a78e865..f389745 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -1413,6 +1413,15 @@ common_handle_option (struct gcc_options *opts,
opts->x_warn_frame_larger_than = value != -1;
break;
+ case OPT_Wshadow:
+ warn_shadow_local = value;
+ warn_shadow_compatible_local = value;
+ break;
+
+ case OPT_Wshadow_local:
+ warn_shadow_compatible_local = value;
+ break;
+
case OPT_Wstrict_aliasing:
set_Wstrict_aliasing (opts, value);
break;
diff --git a/gcc/testsuite/g++.dg/warn/Wshadow-compatible-local-1.C b/gcc/testsuite/g++.dg/warn/Wshadow-compatible-local-1.C
new file mode 100644
index 0000000..e251b72
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wshadow-compatible-local-1.C
@@ -0,0 +1,63 @@
+/* { dg-do compile } */
+/* { dg-options -Wshadow-compatible-local } */
+
+class Bar {
+};
+
+class ChildBar : public Bar {
+};
+
+Bar bar;
+
+class Foo {
+ private:
+ int val;
+
+ public:
+ int func1(int x) {
+ int val;
+ val = x;
+ return val;
+ }
+
+ int func2(int i) { // { dg-warning "shadowed declaration" }
+ int a = 3; // { dg-warning "shadowed declaration" }
+
+ for (int i = 0; i < 5; ++i) { // { dg-warning "shadows a parameter" }
+ for (int i = 0; i < 3; ++i) { // { dg-warning "shadows a previous local" }
+ int a = i; // { dg-warning "shadows a previous local" }
+ func1(a);
+ }
+ }
+
+ return a;
+ }
+
+ int func3() {
+ int bar;
+ float func1 = 0.3;
+ int f = 5; // { dg-warning "shadowed declaration" }
+
+ if (func1 > 1) {
+ float f = 2.0; // { dg-warning "shadows a previous local" }
+ bar = f;
+ }
+ else
+ bar = 1;
+ return bar;
+ }
+
+ void func4() {
+ Bar *bar; // { dg-bogus "shadowed declaration" }
+ ChildBar *cbp; // { dg-bogus "shadowed declaration" }
+ Bar *bp; // { dg-warning "shadowed declaration" }
+ if (val) {
+ int bar; // { dg-bogus "shadows a previous local" }
+ Bar *cbp; // { dg-bogus "shadows a previous local" }
+ ChildBar *bp; // { dg-warning "shadows a previous local" }
+ func1(bar);
+ }
+ }
+};
+
+// { dg-warning "shadowed declaration" "" { target *-*-* } 26 }
diff --git a/gcc/testsuite/g++.dg/warn/Wshadow-local-1.C b/gcc/testsuite/g++.dg/warn/Wshadow-local-1.C
new file mode 100644
index 0000000..24a5bc2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wshadow-local-1.C
@@ -0,0 +1,35 @@
+/* { dg-do compile } */
+/* { dg-options -Wshadow-local } */
+
+struct status
+{
+ int member;
+ void foo2 ();
+
+ inline static int foo3 (int member)
+ {
+ return member;
+ }
+};
+
+int decl1; // { dg-bogus "shadowed declaration" }
+int decl2; // { dg-bogus "shadowed declaration" }
+void foo (struct status &status,
+ double decl1) // { dg-bogus "shadows a global" }
+{
+}
+
+void foo1 (int d)
+{
+ double d; // { dg-error "shadows a parameter" }
+}
+
+void status::foo2 ()
+{
+ int member; // { dg-bogus "shadows a member" }
+ int decl2; // { dg-bogus "shadows a global" }
+ int local; // { dg-warning "shadowed declaration" }
+ {
+ int local; // { dg-warning "shadows a previous local" }
+ }
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wshadow-local-2.C b/gcc/testsuite/g++.dg/warn/Wshadow-local-2.C
new file mode 100644
index 0000000..ac3951e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wshadow-local-2.C
@@ -0,0 +1,63 @@
+/* { dg-do compile } */
+/* { dg-options -Wshadow-local } */
+
+class Bar {
+};
+
+class ChildBar : public Bar {
+};
+
+Bar bar; // { dg-bogus "shadowed declaration" }
+
+class Foo {
+ private:
+ int val;
+
+ public:
+ int func1(int x) {
+ int val; // { dg-bogus "shadows a member" }
+ val = x;
+ return val;
+ }
+
+ int func2(int i) { // { dg-warning "shadowed declaration" }
+ int a = 3; // { dg-warning "shadowed declaration" }
+
+ for (int i = 0; i < 5; ++i) { // { dg-warning "shadows a parameter" }
+ for (int i = 0; i < 3; ++i) { // { dg-warning "shadows a previous local" }
+ int a = i; // { dg-warning "shadows a previous local" }
+ func1(a);
+ }
+ }
+
+ return a;
+ }
+
+ int func3() {
+ int bar; // { dg-bogus "shadows a global" }
+ float func1 = 0.3; // { dg-bogus "shadows a member" }
+ int f = 5; // { dg-warning "shadowed declaration" }
+
+ if (func1 > 1) {
+ float f = 2.0; // { dg-warning "shadows a previous local" }
+ bar = f;
+ }
+ else
+ bar = 1;
+ return bar;
+ }
+
+ void func4() {
+ Bar *bar; // { dg-warning "shadowed declaration" }
+ ChildBar *cbp; // { dg-warning "shadowed declaration" }
+ Bar *bp; // { dg-warning "shadowed declaration" }
+ if (val) {
+ int bar; // { dg-warning "shadows a previous local" }
+ Bar *cbp; // { dg-warning "shadows a previous local" }
+ ChildBar *bp; // { dg-warning "shadows a previous local" }
+ func1(bar);
+ }
+ }
+};
+
+// { dg-warning "shadowed declaration" "" { target *-*-* } 26 }
diff --git a/gcc/testsuite/gcc.dg/Wshadow-compatible-local-1.c b/gcc/testsuite/gcc.dg/Wshadow-compatible-local-1.c
new file mode 100644
index 0000000..cb21be9
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wshadow-compatible-local-1.c
@@ -0,0 +1,36 @@
+/* { dg-do compile } */
+/* { dg-options "-Wshadow-compatible-local" } */
+
+struct Bar {
+};
+
+struct Bar bar; /* { dg-bogus "shadowed declaration" } */
+
+int val; /* { dg-bogus "shadowed declaration" } */
+
+int func1(int x) { /* { dg-bogus "shadowed declaration" } */
+ int val; /* { dg-bogus "shadows a global" } */
+ val = x;
+ return val;
+}
+
+int func2(int i) {
+ int a = 3; /* { dg-warning "shadowed declaration" } */
+ int j; /* { dg-warning "shadowed declaration" } */
+
+ for (j = 0; j < i; ++j) {
+ int a = j; /* { dg-warning "shadows a previous local" } */
+ int j = a + 1; /* { dg-warning "shadows a previous local" } */
+ func1(j);
+ }
+
+ return a;
+}
+
+void func4() {
+ struct Bar bar; /* { dg-bogus "shadowed declaration" } */
+ if (val) {
+ int bar; /* { dg-bogus "shadows a previous local" } */
+ func1(bar);
+ }
+}
diff --git a/gcc/testsuite/gcc.dg/Wshadow-local-1.c b/gcc/testsuite/gcc.dg/Wshadow-local-1.c
new file mode 100644
index 0000000..d0e0dea
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wshadow-local-1.c
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-options "-Wshadow-local" } */
+
+int decl1; /* should not warn */
+void foo (double decl1) /* should not warn */
+{
+}
+
+void foo2 (int d) /* { dg-warning "shadowed declaration" } */
+{
+ {
+ double d; /* { dg-warning "shadows a parameter" } */
+ }
+}
+
+void foo3 ()
+{
+ int local; /* { dg-warning "shadowed declaration" } */
+ {
+ int local; /* { dg-warning "shadows a previous local" } */
+ }
+}
diff --git a/gcc/testsuite/gcc.dg/Wshadow-local-2.c b/gcc/testsuite/gcc.dg/Wshadow-local-2.c
new file mode 100644
index 0000000..9d52fac
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wshadow-local-2.c
@@ -0,0 +1,49 @@
+/* { dg-do compile } */
+/* { dg-options "-Wshadow-local" } */
+
+struct Bar {
+};
+
+struct Bar bar; /* { dg-bogus "shadowed declaration" } */
+
+int val; /* { dg-bogus "shadowed declaration" } */
+
+int func1(int x) { /* { dg-bogus "shadowed declaration" } */
+ int val; /* { dg-bogus "shadows a global" } */
+ val = x;
+ return val;
+}
+
+int func2(int i) {
+ int a = 3; /* { dg-warning "shadowed declaration" } */
+ int j; /* { dg-warning "shadowed declaration" } */
+
+ for (j = 0; j < i; ++j) {
+ int a = j; /* { dg-warning "shadows a previous local" } */
+ int j = a + 1; /* { dg-warning "shadows a previous local" } */
+ func1(j);
+ }
+
+ return a;
+}
+
+int func3() {
+ int bar; /* { dg-bogus "shadows a global" } */
+ float func1 = 0.3; /* { dg-bogus "shadows a global" } */
+
+ if (func1 > 1)
+ bar = 2;
+ else
+ bar = 1;
+ return bar;
+}
+
+void func4() {
+ struct Bar bar; /* { dg-warning "shadowed declaration" } */
+ if (val) {
+ int bar; /* { dg-warning "shadows a previous local" } */
+ func1(bar);
+ }
+}
+
+/* { dg-bogus "shadows a global" "" { target *-*-* } 42 } */
diff --git a/gcc/testsuite/gcc.dg/Wshadow-local-3.c b/gcc/testsuite/gcc.dg/Wshadow-local-3.c
new file mode 100644
index 0000000..429df37
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wshadow-local-3.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-Wno-shadow" } */
+
+void func() {
+ int i;
+ {
+ int i; /* should not warn */
+ }
+}
--
1.7.3.1
--
This patch is available for review at http://codereview.appspot.com/4452058