[pushed] gdb: rank an lvalue argument incompatible for an rvalue parameter
Sourceware to Gerrit sync (Code Review)
gerrit@gnutoolchain-gerrit.osci.io
Mon Dec 9 17:31:00 GMT 2019
The original change was created by Tankut Baris Aktemur.
Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/752
......................................................................
gdb: rank an lvalue argument incompatible for an rvalue parameter
Passing an lvalue argument to a function that takes an rvalue parameter
is not allowed per C++ rules. Consider this function:
int g (int &&x) { return x; }
Calling g as in
int i = 5;
int j = g (i);
is illegal. For instance, GCC 9.2.1 yields
~~~
test.cpp: In function âint main()â:
test.cpp:6:14: error: cannot bind rvalue reference of type âint&&â to
lvalue of type âintâ
6 | int j = g (i);
| ^
~~~
GDB currently allows this function call:
~~~
(gdb) print g(i)
$1 = 5
~~~
Fix this by ranking an lvalue argument incompatible with an rvalue
parameter. The behavior after this patch is:
~~~
(gdb) print g(i)
Cannot resolve function g to any overloaded instance
~~~
Tested with GCC 9.2.1.
gdb/ChangeLog:
2019-12-09 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
* gdbtypes.c (rank_one_type): Return INCOMPATIBLE_TYPE_BADNESS
when ranking an lvalue argument for an rvalue parameter.
gdb/testsuite/ChangeLog:
2019-12-09 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
* gdb.cp/rvalue-ref-overload.cc (g): New function that takes
an rvalue parameter.
* gdb.cp/rvalue-ref-overload.exp: Test calling it with an lvalue
parameter.
Change-Id: I4a6dfc7dac63efa1e3b9f8f391e4b736fbdccdc1
---
M gdb/ChangeLog
M gdb/gdbtypes.c
M gdb/testsuite/ChangeLog
M gdb/testsuite/gdb.cp/rvalue-ref-overload.cc
M gdb/testsuite/gdb.cp/rvalue-ref-overload.exp
5 files changed, 30 insertions(+), 5 deletions(-)
diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 9709d0d..329080e 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2019-12-09 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
+
+ * gdbtypes.c (rank_one_type): Return INCOMPATIBLE_TYPE_BADNESS
+ when ranking an lvalue argument for an rvalue parameter.
+
2019-12-08 Wataru Ashihara <wataash@wataash.com>
* darwin-nat.c (darwin_nat_target::create_inferior): Fix
diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c
index 508628a..0896f71 100644
--- a/gdb/gdbtypes.c
+++ b/gdb/gdbtypes.c
@@ -4303,12 +4303,9 @@
}
else
{
- /* Lvalues should prefer lvalue overloads. */
+ /* It's illegal to pass an lvalue as an rvalue. */
if (TYPE_CODE (parm) == TYPE_CODE_RVALUE_REF)
- {
- rank.subrank = REFERENCE_CONVERSION_RVALUE;
- return sum_ranks (rank, REFERENCE_CONVERSION_BADNESS);
- }
+ return INCOMPATIBLE_TYPE_BADNESS;
}
}
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index bfd686d..123344f 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2019-12-09 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
+
+ * gdb.cp/rvalue-ref-overload.cc (g): New function that takes
+ an rvalue parameter.
+ * gdb.cp/rvalue-ref-overload.exp: Test calling it with an lvalue
+ parameter.
+
2019-12-09 Andrew Burgess <andrew.burgess@embecosm.com>
* gdb.mi/mi-fortran-modules.exp: Add patterns to skip system
diff --git a/gdb/testsuite/gdb.cp/rvalue-ref-overload.cc b/gdb/testsuite/gdb.cp/rvalue-ref-overload.cc
index e3111d5..30634a9 100644
--- a/gdb/testsuite/gdb.cp/rvalue-ref-overload.cc
+++ b/gdb/testsuite/gdb.cp/rvalue-ref-overload.cc
@@ -62,6 +62,12 @@
return 3;
}
+static int
+g (int &&x)
+{
+ return x;
+}
+
int
main ()
{
@@ -78,6 +84,12 @@
int test_const // = 3
= foo_rr_instance1.overloadConst (arg);
+ /* The statement below is illegal: cannot bind rvalue reference of
+ type 'int&&' to lvalue of type 'int'.
+
+ result = g (i); */
+ result = g (5); // this is OK
+
marker1 (); // marker1-returns-here
return result;
}
diff --git a/gdb/testsuite/gdb.cp/rvalue-ref-overload.exp b/gdb/testsuite/gdb.cp/rvalue-ref-overload.exp
index e92e901..cac3d4b 100644
--- a/gdb/testsuite/gdb.cp/rvalue-ref-overload.exp
+++ b/gdb/testsuite/gdb.cp/rvalue-ref-overload.exp
@@ -66,3 +66,7 @@
setup_kfail "c++/15372" "*-*-*"
gdb_test "print f (3)" "3" "rvalue reference overload"
+
+gdb_test "print g (i)" \
+ "Cannot resolve function g to any overloaded instance" \
+ "passing lvalue arg to rvalue parameter"
--
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: I4a6dfc7dac63efa1e3b9f8f391e4b736fbdccdc1
Gerrit-Change-Number: 752
Gerrit-PatchSet: 2
Gerrit-Owner: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Gerrit-Reviewer: Simon Marchi <simon.marchi@polymtl.ca>
Gerrit-Reviewer: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Gerrit-Reviewer: Tom Tromey <tromey@sourceware.org>
Gerrit-MessageType: newpatchset
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