Re: [PATCH] c++: Redundant -Wdeprecated-declarations warning in build_over_call (PR 67960)

[Jason Merrill via Gcc-patches]

On 3/12/20 3:28 PM, Patrick Palka wrote:

In build_over_call, we are emitting a redundant -Wdeprecated-declarations
warning about the deprecated callee function, first from mark_used and again
from build_addr_func <- decay_conversion <- cp_build_addr_expr <- mark_used.

It seems this warning coming from build_addr_func will always be redundant, so
we can safely use a warning_sentinel to disable the warning before calling
build_addr_func.  (And any deprecation warning that could come from
build_addr_func would be for FN, and so we wouldn't be suppressing too much.)

Tested on x86_64-pc-linux-gnu.  Does this look OK to commit?

gcc/cp/ChangeLog:

        PR c++/67960
        * call.c (build_over_call): Use a warning_sentinel to disable
        warn_deprecated_decl before calling build_addr_func.

OK.

gcc/testsuite/ChangeLog:

        PR c++/67960
        g++.dg/diagnostic/pr67960.C: New test.
        g++.dg/diagnostic/pr67960-2.C: New test.
---
  gcc/cp/call.c                               |  5 +++++
  gcc/testsuite/g++.dg/diagnostic/pr67960-2.C | 13 +++++++++++++
  gcc/testsuite/g++.dg/diagnostic/pr67960.C   | 13 +++++++++++++
  3 files changed, 31 insertions(+)
  create mode 100644 gcc/testsuite/g++.dg/diagnostic/pr67960-2.C
  create mode 100644 gcc/testsuite/g++.dg/diagnostic/pr67960.C

diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 5767a8b8c4e..2f6cfd85175 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -9062,6 +9062,11 @@ build_over_call (struct z_candidate *cand, int flags, 
tsubst_flags_t complain)
      }
    else
      {
+      /* If FN is marked deprecated, then we've already issued a deprecated-use
+        warning from mark_used above, so avoid reduntantly issuing another one
+        from build_addr_func.  */
+      warning_sentinel w (warn_deprecated_decl);
+
        fn = build_addr_func (fn, complain);
        if (fn == error_mark_node)
        return error_mark_node;
diff --git a/gcc/testsuite/g++.dg/diagnostic/pr67960-2.C 
b/gcc/testsuite/g++.dg/diagnostic/pr67960-2.C
new file mode 100644
index 00000000000..d2ba509534f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/pr67960-2.C
@@ -0,0 +1,13 @@
+// PR c++/67960
+// { dg-do compile }
+// { dg-additional-options "-Werror -fmax-errors=1" }
+__attribute__((deprecated)) void doNothing(){}
+
+int
+main()
+{
+  doNothing(); // { dg-error "is deprecated" }
+}
+
+// { dg-message "all warnings being treated as errors" "" { target *-*-* } 0 }
+// { dg-bogus "compilation terminated" "" { target *-*-* } 0 }
diff --git a/gcc/testsuite/g++.dg/diagnostic/pr67960.C 
b/gcc/testsuite/g++.dg/diagnostic/pr67960.C
new file mode 100644
index 00000000000..d7b1a2d0811
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/pr67960.C
@@ -0,0 +1,13 @@
+// PR c++/67960
+// { dg-do compile { target c++14 } }
+// { dg-additional-options "-Werror -fmax-errors=1" }
+[[deprecated]] void doNothing(){}
+
+int
+main()
+{
+  doNothing(); // { dg-error "is deprecated" }
+}
+
+// { dg-message "all warnings being treated as errors" "" { target *-*-* } 0 }
+// { dg-bogus "compilation terminated" "" { target *-*-* } 0 }