[PATCH] c++: call complete_type after performing auto deduction [PR80351]

Pokechu22 pokechu022@gmail.com
Thu Mar 24 01:01:20 GMT 2022


When cp_finish_decl calls cp_apply_type_quals_to_decl on a const auto or
constexpr auto variable, the type might not be complete the first time
(this happened when auto deduces to an initializer_list).
cp_apply_type_quals_to_decl removes the const qualifier if the type is
not complete, which is appropriate for grokdeclarator, on the assumption
that the type will be complete when called by cp_finish_decl.

Tested on x86_64 Ubuntu under WSL1 by bootstrapping and comparing results
from 24d51e749570dcb85bd43d3b528f58ad6141de26 with results from this
change.  As far as I can tell, this fixes Wunused-var-38.C and
Wunused-var-39.C without regressions.
(Wunused-var-37.C passed before this change.)

gcc/cp/ChangeLog:

    PR c++/80351
    * decl.cc (cp_finish_decl): Call complete_type after performing
    auto deduction.

gcc/testsuite/ChangeLog:

    PR c++/80351
    * g++.dg/warn/Wunused-var-37.C: New test.
    * g++.dg/warn/Wunused-var-38.C: New test.
    * g++.dg/warn/Wunused-var-39.C: New test.
---
 gcc/cp/decl.cc                             |  2 +-
 gcc/testsuite/g++.dg/warn/Wunused-var-37.C | 64 ++++++++++++++++++++++
 gcc/testsuite/g++.dg/warn/Wunused-var-38.C | 16 ++++++
 gcc/testsuite/g++.dg/warn/Wunused-var-39.C | 16 ++++++
 4 files changed, 97 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/warn/Wunused-var-37.C
 create mode 100644 gcc/testsuite/g++.dg/warn/Wunused-var-38.C
 create mode 100644 gcc/testsuite/g++.dg/warn/Wunused-var-39.C

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 34d9dad9fb0..e382b8ad218 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -8098,7 +8098,7 @@ cp_finish_decl (tree decl, tree init, bool
init_const_expr_p,
       TREE_TYPE (decl) = error_mark_node;
       return;
     }
-      cp_apply_type_quals_to_decl (cp_type_quals (type), decl);
+      cp_apply_type_quals_to_decl (cp_type_quals (complete_type (type)), decl);
     }

   if (ensure_literal_type_for_constexpr_object (decl) == error_mark_node)
diff --git a/gcc/testsuite/g++.dg/warn/Wunused-var-37.C
b/gcc/testsuite/g++.dg/warn/Wunused-var-37.C
new file mode 100644
index 00000000000..54e76ac4e11
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-var-37.C
@@ -0,0 +1,64 @@
+// Tangentially to PR c++/80351
+// { dg-do compile { target c++17 } }
+// { dg-options "-Wunused-variable" }
+#include <initializer_list>
+
+// Warnings:
+static int           int_s1  = 0; // { dg-warning "defined but not used" }
+static int           int_s2  = 0; // { dg-warning "defined but not used" }
+inline static int    int_is1 = 0; // { dg-warning "defined but not used" }
+inline static int    int_is2 = 0; // { dg-warning "defined but not used" }
+// No warnings:
+constexpr static int int_cs1 = 0; // { dg-bogus "defined but not used" }
+constexpr static int int_cs2 = 0; // { dg-bogus "defined but not used" }
+int                  int_1   = 0; // { dg-bogus "defined but not used" }
+int                  int_2   = 0; // { dg-bogus "defined but not used" }
+inline int           int_i1  = 0; // { dg-bogus "defined but not used" }
+inline int           int_i2  = 0; // { dg-bogus "defined but not used" }
+constexpr int        int_c1  = 0; // { dg-bogus "defined but not used" }
+constexpr int        int_c2  = 0; // { dg-bogus "defined but not used" }
+
+// Warnings:
+static auto           int_as1  = 0; // { dg-warning "defined but not used" }
+static auto           int_as2  = 0; // { dg-warning "defined but not used" }
+inline static auto    int_ais1 = 0; // { dg-warning "defined but not used" }
+inline static auto    int_ais2 = 0; // { dg-warning "defined but not used" }
+// No warnings:
+constexpr static auto int_acs1 = 0; // { dg-bogus "defined but not used" }
+constexpr static auto int_acs2 = 0; // { dg-bogus "defined but not used" }
+auto                  int_a1   = 0; // { dg-bogus "defined but not used" }
+auto                  int_a2   = 0; // { dg-bogus "defined but not used" }
+inline auto           int_ai1  = 0; // { dg-bogus "defined but not used" }
+inline auto           int_ai2  = 0; // { dg-bogus "defined but not used" }
+constexpr auto        int_ac1  = 0; // { dg-bogus "defined but not used" }
+constexpr auto        int_ac2  = 0; // { dg-bogus "defined but not used" }
+
+// Warnings:
+static std::initializer_list<int>           il_s1  = {0, 1}; // {
dg-warning "defined but not used" }
+static std::initializer_list<int>           il_s2  = {0, 1}; // {
dg-warning "defined but not used" }
+inline static std::initializer_list<int>    il_is1 = {0, 1}; // {
dg-warning "defined but not used" }
+inline static std::initializer_list<int>    il_is2 = {0, 1}; // {
dg-warning "defined but not used" }
+// No warnings:
+constexpr static std::initializer_list<int> il_cs1 = {0, 1}; // {
dg-bogus "defined but not used" }
+constexpr static std::initializer_list<int> il_cs2 = {0, 1}; // {
dg-bogus "defined but not used" }
+std::initializer_list<int>                  il_1   = {0, 1}; // {
dg-bogus "defined but not used" }
+std::initializer_list<int>                  il_2   = {0, 1}; // {
dg-bogus "defined but not used" }
+inline std::initializer_list<int>           il_i1  = {0, 1}; // {
dg-bogus "defined but not used" }
+inline std::initializer_list<int>           il_i2  = {0, 1}; // {
dg-bogus "defined but not used" }
+constexpr std::initializer_list<int>        il_c1  = {0, 1}; // {
dg-bogus "defined but not used" }
+constexpr std::initializer_list<int>        il_c2  = {0, 1}; // {
dg-bogus "defined but not used" }
+
+// Warnings:
+static auto           il_as1  = {0, 1}; // { dg-warning "defined but
not used" }
+static auto           il_as2  = {0, 1}; // { dg-warning "defined but
not used" }
+inline static auto    il_ais1 = {0, 1}; // { dg-warning "defined but
not used" }
+inline static auto    il_ais2 = {0, 1}; // { dg-warning "defined but
not used" }
+// No warnings:
+constexpr static auto il_acs1 = {0, 1}; // { dg-bogus "defined but not used" }
+constexpr static auto il_acs2 = {0, 1}; // { dg-bogus "defined but not used" }
+auto                  il_a1   = {0, 1}; // { dg-bogus "defined but not used" }
+auto                  il_a2   = {0, 1}; // { dg-bogus "defined but not used" }
+inline auto           il_ai1  = {0, 1}; // { dg-bogus "defined but not used" }
+inline auto           il_ai2  = {0, 1}; // { dg-bogus "defined but not used" }
+constexpr auto        il_ac1  = {0, 1}; // { dg-bogus "defined but not used" }
+constexpr auto        il_ac2  = {0, 1}; // { dg-bogus "defined but not used" }
diff --git a/gcc/testsuite/g++.dg/warn/Wunused-var-38.C
b/gcc/testsuite/g++.dg/warn/Wunused-var-38.C
new file mode 100644
index 00000000000..3d34bc8e8c1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-var-38.C
@@ -0,0 +1,16 @@
+// PR c++/80351
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wunused-variable" }
+#include <initializer_list>
+
+constexpr auto int_1 = 1; // { dg-bogus "defined but not used" }
+constexpr auto int_2 = 2; // { dg-bogus "defined but not used" }
+
+constexpr auto il_int_1 = {3, 3}; // { dg-bogus "defined but not
used" "Triggered by PR80351" }
+constexpr auto il_int_2 = {4, 4}; // { dg-bogus "defined but not
used" "Not triggered by PR80351" }
+
+constexpr auto il_uint_1 = {5u, 5u}; // { dg-bogus "defined but not
used" "Triggered by PR80351" }
+constexpr auto il_uint_2 = {6u, 6u}; // { dg-bogus "defined but not
used" "Not triggered by PR80351" }
+
+constexpr auto uint_1 = 7u; // { dg-bogus "defined but not used" }
+constexpr auto uint_2 = 8u; // { dg-bogus "defined but not used" }
diff --git a/gcc/testsuite/g++.dg/warn/Wunused-var-39.C
b/gcc/testsuite/g++.dg/warn/Wunused-var-39.C
new file mode 100644
index 00000000000..d25a74c43c2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-var-39.C
@@ -0,0 +1,16 @@
+// PR c++/80351
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wunused-variable" }
+#include <initializer_list>
+
+const auto int_1 = 1; // { dg-bogus "defined but not used" }
+const auto int_2 = 2; // { dg-bogus "defined but not used" }
+
+const auto il_int_1 = {3, 3}; // { dg-bogus "defined but not used"
"Triggered by PR80351" }
+const auto il_int_2 = {4, 4}; // { dg-bogus "defined but not used"
"Not triggered by PR80351" }
+
+const auto il_uint_1 = {5u, 5u}; // { dg-bogus "defined but not used"
"Triggered by PR80351" }
+const auto il_uint_2 = {6u, 6u}; // { dg-bogus "defined but not used"
"Not triggered by PR80351" }
+
+const auto uint_1 = 7u; // { dg-bogus "defined but not used" }
+const auto uint_2 = 8u; // { dg-bogus "defined but not used" }
-- 
2.25.1


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