This adds a warning switch for the existing "returning address of
local variable" warnings in the C and C++ FEs which are enabled by
default but have no switch controlling them. Adding a switch allows it
to be turned into an error with -Werror=return-local-addr. I've added
two tests checking the -Werror form works.
gcc/c-family:
PR c++/54930
* c.opt (Wreturn_local_addr): Define new option.
gcc/c:
PR c++/54930
* c-typeck.c (c_finish_return): Use OPT_Wreturn_local_addr.
gcc/cp:
PR c++/54930
* typeck.c (maybe_warn_about_returning_address_of_local): Use
OPT_Wreturn_local_addr.
gcc:
PR c++/54930
* doc/invoke.texi (Warning Options): Document -Wno-return-local-addr.
gcc/testsuite:
PR c++/54930
* gcc.dg/Wreturn-local-addr.c: New.
* g++.dg/warn/Wno-return-local-addr.C: New.
* g++.dg/warn/Wreturn-local-addr.C: New.
Tested x86_64-linux, OK for trunk?
commit 77abe727e837e052680be8020fa2990cce4d1e9a
Author: Jonathan Wakely <jwakely....@gmail.com>
Date: Wed Oct 17 19:32:10 2012 +0100
gcc/c-family:
PR c++/54930
* c.opt (Wreturn_local_addr): Define new option.
gcc/c:
PR c++/54930
* c-typeck.c (c_finish_return): Use OPT_Wreturn_local_addr.
gcc/cp:
PR c++/54930
* typeck.c (maybe_warn_about_returning_address_of_local): Use
OPT_Wreturn_local_addr.
gcc:
PR c++/54930
* doc/invoke.texi (Warning Options): Document -Wno-return-local-addr.
gcc/testsuite:
PR c++/54930
* gcc.dg/Wreturn-local-addr.c: New.
* g++.dg/warn/Wno-return-local-addr.C: New.
* g++.dg/warn/Wreturn-local-addr.C: New.
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 3166984..f75b58c 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -601,6 +601,10 @@ Wreorder
C++ ObjC++ Var(warn_reorder) Warning LangEnabledBy(C++ ObjC++,Wall)
Warn when the compiler reorders code
+Wreturn-local-addr
+C ObjC C++ ObjC++ Var(warn_return_local_addr) Init(1) Warning
+Warn about returning a pointer/reference to a local or temporary variable.
+
Wreturn-type
C ObjC C++ ObjC++ Var(warn_return_type) Warning
Warn whenever a function's return type defaults to \"int\" (C), or about
inconsistent return types (C++)
diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index 4855933..cf63355 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -8742,7 +8742,8 @@ c_finish_return (location_t loc, tree retval, tree
origtype)
&& !TREE_STATIC (inner)
&& DECL_CONTEXT (inner) == current_function_decl)
warning_at (loc,
- 0, "function returns address of local variable");
+ OPT_Wreturn_local_addr, "function returns address "
+ "of local variable");
break;
default:
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index eaa0935..d2944d3 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -8019,14 +8019,14 @@ maybe_warn_about_returning_address_of_local (tree
retval)
if (TREE_CODE (whats_returned) == AGGR_INIT_EXPR
|| TREE_CODE (whats_returned) == TARGET_EXPR)
{
- warning (0, "returning reference to temporary");
+ warning (OPT_Wreturn_local_addr, "returning reference to temporary");
return;
}
if (TREE_CODE (whats_returned) == VAR_DECL
&& DECL_NAME (whats_returned)
&& TEMP_NAME_P (DECL_NAME (whats_returned)))
{
- warning (0, "reference to non-lvalue returned");
+ warning (OPT_Wreturn_local_addr, "reference to non-lvalue returned");
return;
}
}
@@ -8042,10 +8042,10 @@ maybe_warn_about_returning_address_of_local (tree
retval)
|| TREE_PUBLIC (whats_returned)))
{
if (TREE_CODE (valtype) == REFERENCE_TYPE)
- warning (0, "reference to local variable %q+D returned",
+ warning (OPT_Wreturn_local_addr, "reference to local variable %q+D
returned",
whats_returned);
else
- warning (0, "address of local variable %q+D returned",
+ warning (OPT_Wreturn_local_addr, "address of local variable %q+D
returned",
whats_returned);
return;
}
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index f8c9230..2e36de1 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -261,7 +261,7 @@ Objective-C and Objective-C++ Dialects}.
-Woverlength-strings -Wpacked -Wpacked-bitfield-compat -Wpadded @gol
-Wparentheses -Wpedantic-ms-format -Wno-pedantic-ms-format @gol
-Wpointer-arith -Wno-pointer-to-int-cast @gol
--Wredundant-decls @gol
+-Wredundant-decls -Wno-return-local-addr @gol
-Wreturn-type -Wsequence-point -Wshadow @gol
-Wsign-compare -Wsign-conversion -Wsizeof-pointer-memaccess @gol
-Wstack-protector -Wstack-usage=@var{len} -Wstrict-aliasing @gol
@@ -3526,6 +3526,12 @@ definitions, may be found on the GCC readings page, at
This warning is enabled by @option{-Wall} for C and C++.
+@item -Wno-return-local-addr
+@opindex Wno-return-local-addr
+@opindex Wreturn-local-addr
+Do not warn about returning a pointer (or in C++, a reference) to a
+variable that goes out of scope after the function returns.
+
@item -Wreturn-type
@opindex Wreturn-type
@opindex Wno-return-type
diff --git a/gcc/testsuite/g++.dg/warn/Wno-return-local-addr.C
b/gcc/testsuite/g++.dg/warn/Wno-return-local-addr.C
new file mode 100644
index 0000000..e15bfa2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wno-return-local-addr.C
@@ -0,0 +1,26 @@
+// { dg-do assemble }
+// { dg-options "-Wno-return-local-addr" }
+
+int& bad1()
+{
+ int x = 0;
+ return x;
+}
+
+int* bad2()
+{
+ int x = 0;
+ return &x;
+}
+
+int f();
+
+const int& bad3()
+{
+ return f();
+}
+
+const int& bad4()
+{
+ return int();
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wreturn-local-addr.C
b/gcc/testsuite/g++.dg/warn/Wreturn-local-addr.C
new file mode 100644
index 0000000..faa3a34
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wreturn-local-addr.C
@@ -0,0 +1,20 @@
+// { dg-do assemble }
+// { dg-options "-Werror=return-local-addr" }
+// { dg-message "some warnings being treated as errors" "" {target "*-*-*"} 0 }
+
+int& bad1()
+{
+ int x = 0; // { dg-error "reference to local variable" }
+ return x;
+}
+
+int* bad2()
+{
+ int x = 0; // { dg-error "address of local variable" }
+ return &x;
+}
+
+const int& bad4()
+{
+ return int(); // { dg-error "returning reference to
temporary" }
+}
diff --git a/gcc/testsuite/gcc.dg/Wreturn-local-addr.c
b/gcc/testsuite/gcc.dg/Wreturn-local-addr.c
new file mode 100644
index 0000000..d496d20
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wreturn-local-addr.c
@@ -0,0 +1,9 @@
+/* { dg-do assemble } */
+/* { dg-options "-Werror=return-local-addr" } */
+/* { dg-message "some warnings being treated as errors" "" {target "*-*-*"} 0
} */
+
+int* bad()
+{
+ int x = 0;
+ return &x; /* { dg-error "address of local variable" } */
+}
