On 10/28/20 2:00 PM, Marek Polacek wrote:
On Tue, Oct 27, 2020 at 01:36:30PM -0400, Jason Merrill wrote:
On 10/24/20 6:52 PM, Marek Polacek wrote:
Here, in r11-155, I changed the call to uses_template_parms to
type_dependent_expression_p_push to avoid a crash in C++98 in
value_dependent_expression_p on a non-constant expression. But that
prompted a host of complaints that we now warn for value-dependent
expressions in templates. Those warnings are technically valid, but
people still don't want them because they're awkward to avoid. So let's
partially revert my earlier fix and make sure that we don't ICE in
value_dependent_expression_p by checking potential_constant_expression
first.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/10?
gcc/cp/ChangeLog:
PR c++/96675
PR c++/96742
* pt.c (tsubst_copy_and_build): Call uses_template_parms instead of
type_dependent_expression_p_push. Only call uses_template_parms
for expressions that are potential_constant_expression.
gcc/testsuite/ChangeLog:
PR c++/96675
PR c++/96742
* g++.dg/warn/Wdiv-by-zero-3.C: Turn dg-warning into dg-bogus.
* g++.dg/warn/Wtautological-compare3.C: New test.
* g++.dg/warn/Wtype-limits5.C: New test.
* g++.old-deja/g++.pt/crash10.C: Remove dg-warning.
---
gcc/cp/pt.c | 6 ++++--
gcc/testsuite/g++.dg/warn/Wdiv-by-zero-3.C | 6 ++++--
gcc/testsuite/g++.dg/warn/Wtautological-compare3.C | 11 +++++++++++
gcc/testsuite/g++.dg/warn/Wtype-limits5.C | 11 +++++++++++
gcc/testsuite/g++.old-deja/g++.pt/crash10.C | 1 -
5 files changed, 30 insertions(+), 5 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/warn/Wtautological-compare3.C
create mode 100644 gcc/testsuite/g++.dg/warn/Wtype-limits5.C
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index dc664ec3798..8aa0bc2c0d8 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -19618,8 +19618,10 @@ tsubst_copy_and_build (tree t,
{
/* If T was type-dependent, suppress warnings that depend on the range
of the types involved. */
- bool was_dep = type_dependent_expression_p_push (t);
-
+ ++processing_template_decl;
+ const bool was_dep = (!potential_constant_expression (t)
+ || uses_template_parms (t));
We don't want to suppress warnings for a non-constant expression that uses
no template parms. So maybe
Fair enough.
potential_c_e ? value_d : type_d
That works for all the cases I have.
? Or perhaps instantiation_dependent_expression_p.
i_d_e_p would still crash in C++98 :(.
Perhaps we should protect the value_d call in i_d_e_p with potential_c_e?
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/10?
OK.
-- >8 --
Here, in r11-155, I changed the call to uses_template_parms to
type_dependent_expression_p_push to avoid a crash in C++98 in
value_dependent_expression_p on a non-constant expression. But that
prompted a host of complaints that we now warn for value-dependent
expressions in templates. Those warnings are technically valid, but
people still don't want them because they're awkward to avoid. This
patch uses value_dependent_expression_p or type_dependent_expression_p.
But make sure that we don't ICE in value_dependent_expression_p by
checking potential_constant_expression first.
gcc/cp/ChangeLog:
PR c++/96675
PR c++/96742
* pt.c (tsubst_copy_and_build): Call value_dependent_expression_p or
type_dependent_expression_p instead of type_dependent_expression_p_push.
But only call value_dependent_expression_p for expressions that are
potential_constant_expression.
gcc/testsuite/ChangeLog:
PR c++/96675
PR c++/96742
* g++.dg/warn/Wdiv-by-zero-3.C: Turn dg-warning into dg-bogus.
* g++.dg/warn/Wtautological-compare3.C: New test.
* g++.dg/warn/Wtype-limits5.C: New test.
* g++.old-deja/g++.pt/crash10.C: Remove dg-warning.
---
gcc/cp/pt.c | 7 +++++--
gcc/testsuite/g++.dg/warn/Wdiv-by-zero-3.C | 6 ++++--
gcc/testsuite/g++.dg/warn/Wtautological-compare3.C | 11 +++++++++++
gcc/testsuite/g++.dg/warn/Wtype-limits5.C | 11 +++++++++++
gcc/testsuite/g++.old-deja/g++.pt/crash10.C | 1 -
5 files changed, 31 insertions(+), 5 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/warn/Wtautological-compare3.C
create mode 100644 gcc/testsuite/g++.dg/warn/Wtype-limits5.C
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 3c0f2546489..57db476645e 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -19618,8 +19618,11 @@ tsubst_copy_and_build (tree t,
{
/* If T was type-dependent, suppress warnings that depend on the range
of the types involved. */
- bool was_dep = type_dependent_expression_p_push (t);
-
+ ++processing_template_decl;
+ const bool was_dep = (potential_constant_expression (t)
+ ? value_dependent_expression_p (t)
+ : type_dependent_expression_p (t));
+ --processing_template_decl;
tree op0 = RECUR (TREE_OPERAND (t, 0));
tree op1 = RECUR (TREE_OPERAND (t, 1));
diff --git a/gcc/testsuite/g++.dg/warn/Wdiv-by-zero-3.C b/gcc/testsuite/g++.dg/warn/Wdiv-by-zero-3.C
index 424eb0c3d49..01f691f2878 100644
--- a/gcc/testsuite/g++.dg/warn/Wdiv-by-zero-3.C
+++ b/gcc/testsuite/g++.dg/warn/Wdiv-by-zero-3.C
@@ -5,8 +5,10 @@ foo (T t, int i)
{
int m1 = 10 / t;
int m2 = 10 / i;
- int m3 = 10 / (sizeof(T) - sizeof(int)); // { dg-warning "division by" }
- int m4 = 10 / N; // { dg-warning "division by" }
+ // People don't want to see warnings for type- or value-dependent
+ // expressions.
+ int m3 = 10 / (sizeof(T) - sizeof(int)); // { dg-bogus "division by" }
+ int m4 = 10 / N; // { dg-bogus "division by" }
return m1 + m2 + m3 + m4;
}
diff --git a/gcc/testsuite/g++.dg/warn/Wtautological-compare3.C b/gcc/testsuite/g++.dg/warn/Wtautological-compare3.C
new file mode 100644
index 00000000000..89bf1b619a6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wtautological-compare3.C
@@ -0,0 +1,11 @@
+// PR c++/96675
+// { dg-do compile { target c++11 } }
+// { dg-additional-options "-Wtautological-compare" }
+
+template<char c>
+constexpr bool f(char d) {
+ return 'a' <= c && c <= 'z' ? (d | 0x20) == c :
+ 'A' <= c && c <= 'Z' ? (d & ~0x20) == c :
+ d == c;
+}
+static_assert(f<'p'>('P'), "");
diff --git a/gcc/testsuite/g++.dg/warn/Wtype-limits5.C
b/gcc/testsuite/g++.dg/warn/Wtype-limits5.C
new file mode 100644
index 00000000000..5e79123b622
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wtype-limits5.C
@@ -0,0 +1,11 @@
+// PR c++/96742
+// { dg-additional-options "-Wtype-limits" }
+
+template <unsigned N>
+bool f(unsigned x) {
+ return unsigned(x < N);
+}
+
+int main() {
+ f<0>(1);
+}
diff --git a/gcc/testsuite/g++.old-deja/g++.pt/crash10.C
b/gcc/testsuite/g++.old-deja/g++.pt/crash10.C
index 012e3d0c11b..a84b19004ee 100644
--- a/gcc/testsuite/g++.old-deja/g++.pt/crash10.C
+++ b/gcc/testsuite/g++.old-deja/g++.pt/crash10.C
@@ -6,7 +6,6 @@ public:
enum { val = (N == 0) ? M : GCD<N, M % N>::val };
// { dg-error "constant expression" "valid" { target *-*-* } .-1 }
// { dg-message "template argument" "valid" { target *-*-* } .-2 }
-// { dg-warning "division by" "" { target *-*-* } .-3 }
};
int main() {
base-commit: 176b8b9679dfec881b7cf379f808cca3950b1e74
