So, my suggestion would be to warn for any call with a nonzero value.
The current documentation says that you should only use nonzero values
for debug purposes. A warning would help yes, how many people read the
manual after all :-)
Thank you both for the feedback. Attached is a simplified patch
to issue a warning for all builtin_xxx_address calls with any
non-zero argument.
Martin
gcc/ChangeLog
2015-07-27 Martin Sebor <mse...@redhat.com>
* c-family/c.opt (-Wbuiltin-address): New warning option.
* doc/invoke.texi (Wbuiltin-address): Document it.
* doc/extend.texi (__builtin_frame_addrress, __builtin_return_addrress):
Clarify possible effects of calling the functions with non-zero
arguments and mention -Wbuiltin-address.
* builtins.c (expand_builtin_frame_address): Handle -Wbuiltin-address.
gcc/testsuite/ChangeLog
2015-07-27 Martin Sebor <mse...@redhat.com>
* g++.dg/Wbuiltin-address-in-Wall.C: New test.
* g++.dg/Wbuiltin-address.C: New test.
* g++.dg/Wno-builtin-address.C: New test.
* gcc.dg/Wbuiltin-address-in-Wall.c: New test.
* gcc.dg/Wbuiltin-address.c: New test.
* gcc.dg/Wno-builtin-address.c: New test.
diff --git a/gcc/builtins.c b/gcc/builtins.c
index e8fe3db..48379f8 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -4564,34 +4564,38 @@ expand_builtin_frame_address (tree fndecl, tree exp)
{
/* The argument must be a nonnegative integer constant.
It counts the number of frames to scan up the stack.
- The value is the return address saved in that frame. */
+ The value is either the frame pointer value or the return
+ address saved in that frame. */
if (call_expr_nargs (exp) == 0)
/* Warning about missing arg was already issued. */
return const0_rtx;
else if (! tree_fits_uhwi_p (CALL_EXPR_ARG (exp, 0)))
{
- if (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_FRAME_ADDRESS)
- error ("invalid argument to %<__builtin_frame_address%>");
- else
- error ("invalid argument to %<__builtin_return_address%>");
+ error ("invalid argument to %qD", fndecl);
return const0_rtx;
}
else
{
- rtx tem
- = expand_builtin_return_addr (DECL_FUNCTION_CODE (fndecl),
- tree_to_uhwi (CALL_EXPR_ARG (exp, 0)));
+ /* Number of frames to scan up the stack. */
+ const unsigned HOST_WIDE_INT count = tree_to_uhwi (CALL_EXPR_ARG (exp, 0));
+
+ rtx tem = expand_builtin_return_addr (DECL_FUNCTION_CODE (fndecl), count);
/* Some ports cannot access arbitrary stack frames. */
if (tem == NULL)
{
- if (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_FRAME_ADDRESS)
- warning (0, "unsupported argument to %<__builtin_frame_address%>");
- else
- warning (0, "unsupported argument to %<__builtin_return_address%>");
+ warning (0, "invalid argument to %qD", fndecl);
return const0_rtx;
}
+ if (0 < count)
+ {
+ /* Warn since no effort is made to ensure that any frame
+ beyond the current one exists or can be safely reached. */
+ warning (OPT_Wbuiltin_address, "calling %qD with "
+ "a non-zero argument is unsafe", fndecl);
+ }
+
/* For __builtin_frame_address, return what we've got. */
if (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_FRAME_ADDRESS)
return tem;
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 285952e..bdff624 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -295,6 +295,10 @@ Wbool-compare
C ObjC C++ ObjC++ Var(warn_bool_compare) Warning LangEnabledBy(C ObjC C++ ObjC++,Wall)
Warn about boolean expression compared with an integer value different from true/false
+Wbuiltin-address
+C ObjC C++ ObjC++ Var(warn_builtin_address) Warning LangEnabledBy(C ObjC C++ ObjC++,Wall)
+Warn when __builtin_frame_address or __builtin_return_address is used unsafely
+
Wbuiltin-macro-redefined
C ObjC C++ ObjC++ CPP(warn_builtin_macro_redefined) CppReason(CPP_W_BUILTIN_MACRO_REDEFINED) Var(cpp_warn_builtin_macro_redefined) Init(1) Warning
Warn when a built-in preprocessor macro is undefined or redefined
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 9ad2b68..1b4596c 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -8562,8 +8562,11 @@ to determine if the top of the stack has been reached.
Additional post-processing of the returned value may be needed, see
@code{__builtin_extract_return_addr}.
-This function should only be used with a nonzero argument for debugging
-purposes.
+Calling this function with a nonzero argument can have unpredictable
+effects, including crashing the calling program. As a result, calls
+that are considered unsafe are diagnosed when the @option{-Wbuiltin-address}
+option is in effect. Such calls are typically only useful in debugging
+situations.
@end deftypefn
@deftypefn {Built-in Function} {void *} __builtin_extract_return_addr (void *@var{addr})
@@ -8601,8 +8604,11 @@ any function other than the current one; in such cases, or when the top
of the stack has been reached, this function returns @code{0} if
the first frame pointer is properly initialized by the startup code.
-This function should only be used with a nonzero argument for debugging
-purposes.
+Calling this function with a nonzero argument can have unpredictable
+effects, including crashing the calling program. As a result, calls
+that are considered unsafe are diagnosed when the @option{-Wbuiltin-address}
+option is in effect. Such calls are typically only useful in debugging
+situations.
@end deftypefn
@node Vector Extensions
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 5903c75..4e64108 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -241,7 +241,7 @@ Objective-C and Objective-C++ Dialects}.
-pedantic-errors @gol
-w -Wextra -Wall -Waddress -Waggregate-return @gol
-Waggressive-loop-optimizations -Warray-bounds -Warray-bounds=@var{n} @gol
--Wbool-compare @gol
+-Wbool-compare -Wbuiltin-address @gol
-Wno-attributes -Wno-builtin-macro-redefined @gol
-Wc90-c99-compat -Wc99-c11-compat @gol
-Wc++-compat -Wc++11-compat -Wc++14-compat -Wcast-align -Wcast-qual @gol
@@ -4436,6 +4436,13 @@ if ((n > 1) == 2) @{ @dots{} @}
@end smallexample
This warning is enabled by @option{-Wall}.
+@item -Wbuiltin-address
+@opindex Wno-builtin-address
+@opindex Wbuiltin-address
+Warn when the @samp{__builtin_frame_address} or @samp{__builtin_return_address}
+is called with an argument greater than 0. Such calls may return indeterminate
+values or crash the program. The warning is included in @option{-Wall}.
+
@item -Wno-discarded-qualifiers @r{(C and Objective-C only)}
@opindex Wno-discarded-qualifiers
@opindex Wdiscarded-qualifiers
diff --git a/gcc/testsuite/g++.dg/Wbuiltin-address-in-Wall.C b/gcc/testsuite/g++.dg/Wbuiltin-address-in-Wall.C
new file mode 100644
index 0000000..aa9e17f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/Wbuiltin-address-in-Wall.C
@@ -0,0 +1,14 @@
+// { dg-do compile }
+// { dg-options "-Wall" }
+
+// Verify that -Wbuiltin-address is included in -Wall.
+
+void* test_builtin_address (unsigned i)
+{
+ void* const ba[] = {
+ __builtin_frame_address (4), // { dg-warning "builtin_frame_address" }
+ __builtin_return_address (4) // { dg-warning "builtin_return_address" }
+ };
+
+ return ba [i];
+}
diff --git a/gcc/testsuite/g++.dg/Wbuiltin-address.C b/gcc/testsuite/g++.dg/Wbuiltin-address.C
new file mode 100644
index 0000000..5e6ff74
--- /dev/null
+++ b/gcc/testsuite/g++.dg/Wbuiltin-address.C
@@ -0,0 +1,70 @@
+// { dg-do compile }
+// { dg-options "-Wbuiltin-address" }
+
+static void* const fa[] = {
+ __builtin_frame_address (0),
+ __builtin_frame_address (1), // { dg-warning "builtin_frame_address" }
+ __builtin_frame_address (2), // { dg-warning "builtin_frame_address" }
+ __builtin_frame_address (3), // { dg-warning "builtin_frame_address" }
+ __builtin_frame_address (4) // { dg-warning "builtin_frame_address" }
+};
+
+
+static void* const ra[] = {
+ __builtin_return_address (0),
+ __builtin_return_address (1), // { dg-warning "builtin_return_address" }
+ __builtin_return_address (2), // { dg-warning "builtin_return_address" }
+ __builtin_return_address (3), // { dg-warning "builtin_return_address" }
+ __builtin_return_address (4) // { dg-warning "builtin_return_address" }
+};
+
+
+void* __attribute__ ((weak))
+test_builtin_frame_address (unsigned i)
+{
+ void* const fa[] = {
+ __builtin_frame_address (0),
+ __builtin_frame_address (1), // { dg-warning "builtin_frame_address" }
+ __builtin_frame_address (2), // { dg-warning "builtin_frame_address" }
+ __builtin_frame_address (3), // { dg-warning "builtin_frame_address" }
+ __builtin_frame_address (4) // { dg-warning "builtin_frame_address" }
+ };
+
+ return fa [i];
+}
+
+
+void* __attribute__ ((weak))
+test_builtin_return_address (unsigned i)
+{
+ void* const ra[] = {
+ __builtin_return_address (0),
+ __builtin_return_address (1), // { dg-warning "builtin_return_address" }
+ __builtin_return_address (2), // { dg-warning "builtin_return_address" }
+ __builtin_return_address (3), // { dg-warning "builtin_return_address" }
+ __builtin_return_address (4) // { dg-warning "builtin_return_address" }
+ };
+ return ra [i];
+}
+
+
+int main ()
+{
+ test_builtin_frame_address (0);
+
+ test_builtin_return_address (0);
+
+ void* const a[] = {
+ __builtin_frame_address (0),
+ __builtin_frame_address (1), // { dg-warning "builtin_frame_address" }
+ __builtin_frame_address (2), // { dg-warning "builtin_frame_address" }
+ __builtin_frame_address (3), // { dg-warning "builtin_frame_address" }
+ __builtin_frame_address (4), // { dg-warning "builtin_frame_address" }
+
+ __builtin_return_address (0),
+ __builtin_return_address (1), // { dg-warning "builtin_return_address" }
+ __builtin_return_address (2), // { dg-warning "builtin_return_address" }
+ __builtin_return_address (3), // { dg-warning "builtin_return_address" }
+ __builtin_return_address (4) // { dg-warning "builtin_return_address" }
+ };
+}
diff --git a/gcc/testsuite/g++.dg/Wno-builtin-address.C b/gcc/testsuite/g++.dg/Wno-builtin-address.C
new file mode 100644
index 0000000..a460649
--- /dev/null
+++ b/gcc/testsuite/g++.dg/Wno-builtin-address.C
@@ -0,0 +1,6 @@
+// { dg-do compile }
+// { dg-options "-Werror" }
+
+// Verify that -Wbuiltin-address is not enabled by default by enabling
+// -Werror and verifying the test still compiles.
+#include "Wbuiltin-address.C"
diff --git a/gcc/testsuite/gcc.dg/Wbuiltin-address-in-Wall.c b/gcc/testsuite/gcc.dg/Wbuiltin-address-in-Wall.c
new file mode 100644
index 0000000..9f73810
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wbuiltin-address-in-Wall.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-Wall" } */
+
+/* Verify that -Wbuiltin-address is included in -Wall. */
+
+void* test_builtin_address (unsigned i)
+{
+ void* const ba[] = {
+ __builtin_frame_address (4), /* { dg-warning "builtin_frame_address" } */
+ __builtin_return_address (4) /* { dg-warning "builtin_return_address" } */
+ };
+
+ return ba [i];
+}
diff --git a/gcc/testsuite/gcc.dg/Wbuiltin-address.c b/gcc/testsuite/gcc.dg/Wbuiltin-address.c
new file mode 100644
index 0000000..5483f5d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wbuiltin-address.c
@@ -0,0 +1,54 @@
+/* { dg-do compile } */
+/* { dg-options "-Wbuiltin-address" } */
+
+void* __attribute__ ((weak))
+test_builtin_frame_address (unsigned i)
+{
+ void* const fa[] = {
+ __builtin_frame_address (0),
+ __builtin_frame_address (1), /* { dg-warning "builtin_frame_address" } */
+ __builtin_frame_address (2), /* { dg-warning "builtin_frame_address" } */
+ __builtin_frame_address (3), /* { dg-warning "builtin_frame_address" } */
+ __builtin_frame_address (4) /* { dg-warning "builtin_frame_address" } */
+ };
+
+ return fa [i];
+}
+
+
+void* __attribute__ ((weak))
+test_builtin_return_address (unsigned i)
+{
+ void* const ra[] = {
+ __builtin_return_address (0),
+ __builtin_return_address (1), /* { dg-warning "builtin_return_address" } */
+ __builtin_return_address (2), /* { dg-warning "builtin_return_address" } */
+ __builtin_return_address (3), /* { dg-warning "builtin_return_address" } */
+ __builtin_return_address (4) /* { dg-warning "builtin_return_address" } */
+ };
+ return ra [i];
+}
+
+
+int main (void)
+{
+ test_builtin_frame_address (0);
+
+ test_builtin_return_address (0);
+
+ void* const a[] = {
+ __builtin_frame_address (0),
+ __builtin_frame_address (1), /* { dg-warning "builtin_frame_address" } */
+ __builtin_frame_address (2), /* { dg-warning "builtin_frame_address" } */
+ __builtin_frame_address (3), /* { dg-warning "builtin_frame_address" } */
+ __builtin_frame_address (4), /* { dg-warning "builtin_frame_address" } */
+
+ __builtin_return_address (0),
+ __builtin_return_address (1), /* { dg-warning "builtin_return_address" } */
+ __builtin_return_address (2), /* { dg-warning "builtin_return_address" } */
+ __builtin_return_address (3), /* { dg-warning "builtin_return_address" } */
+ __builtin_return_address (4) /* { dg-warning "builtin_return_address" } */
+ };
+
+ return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/Wno-builtin-address.c b/gcc/testsuite/gcc.dg/Wno-builtin-address.c
new file mode 100644
index 0000000..c2724d1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wno-builtin-address.c
@@ -0,0 +1,6 @@
+/* { dg-do compile } */
+/* { dg-options "-Werror" } */
+
+/* Verify that -Wbuiltin-address is not enabled by default by enabling
+ -Werror and verifying the test still compiles. */
+#include "Wbuiltin-address.c"
