diff mbox series

c++: Don't hide narrowing errors in system headers

Message ID 20210716000344.1034784-1-polacek@redhat.com
State New
Headers show
Series c++: Don't hide narrowing errors in system headers | expand

Commit Message

Marek Polacek July 16, 2021, 12:03 a.m. UTC 
Jonathan pointed me at this issue where

  constexpr unsigned f() { constexpr int n = -1; return unsigned{n}; }

is accepted in system headers, despite the narrowing conversion from
a constant.  I suspect that whereas narrowing warnings should be
disabled, ill-formed narrowing of constants should be a hard error
(which can still be disabled by -Wno-narrowing).

Bootstrapped/regtested on {ppc64le,x86_64}-pc-linux-gnu, ok for trunk?

gcc/cp/ChangeLog:

	* typeck2.c (check_narrowing): Don't suppress the pedantic error
	in system headers.

libstdc++-v3/ChangeLog:

	* testsuite/20_util/ratio/operations/ops_overflow_neg.cc: Add
	dg-error.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1y/Wnarrowing2.C: New test.
	* g++.dg/cpp1y/Wnarrowing2.h: New test.
---
 gcc/cp/typeck2.c                                              | 1 +
 gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.C                      | 4 ++++
 gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.h                      | 2 ++
 .../testsuite/20_util/ratio/operations/ops_overflow_neg.cc    | 2 ++
 4 files changed, 9 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.C
 create mode 100644 gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.h


base-commit: f364cdffa47af574f90f671b2dcf5afa91442741

Comments

Jason Merrill July 16, 2021, 1:01 p.m. UTC | #1 
On 7/15/21 8:03 PM, Marek Polacek wrote:
> Jonathan pointed me at this issue where
> 
>    constexpr unsigned f() { constexpr int n = -1; return unsigned{n}; }
> 
> is accepted in system headers, despite the narrowing conversion from
> a constant.  I suspect that whereas narrowing warnings should be
> disabled, ill-formed narrowing of constants should be a hard error
> (which can still be disabled by -Wno-narrowing).
> 
> Bootstrapped/regtested on {ppc64le,x86_64}-pc-linux-gnu, ok for trunk?

OK.

> gcc/cp/ChangeLog:
> 
> 	* typeck2.c (check_narrowing): Don't suppress the pedantic error
> 	in system headers.
> 
> libstdc++-v3/ChangeLog:
> 
> 	* testsuite/20_util/ratio/operations/ops_overflow_neg.cc: Add
> 	dg-error.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp1y/Wnarrowing2.C: New test.
> 	* g++.dg/cpp1y/Wnarrowing2.h: New test.
> ---
>   gcc/cp/typeck2.c                                              | 1 +
>   gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.C                      | 4 ++++
>   gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.h                      | 2 ++
>   .../testsuite/20_util/ratio/operations/ops_overflow_neg.cc    | 2 ++
>   4 files changed, 9 insertions(+)
>   create mode 100644 gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.C
>   create mode 100644 gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.h
> 
> diff --git a/gcc/cp/typeck2.c b/gcc/cp/typeck2.c
> index 6679e247816..dcfdff2f905 100644
> --- a/gcc/cp/typeck2.c
> +++ b/gcc/cp/typeck2.c
> @@ -986,6 +986,7 @@ check_narrowing (tree type, tree init, tsubst_flags_t complain,
>   	{
>   	  int savederrorcount = errorcount;
>   	  global_dc->pedantic_errors = 1;
> +	  auto s = make_temp_override (global_dc->dc_warn_system_headers, true);
>   	  pedwarn (loc, OPT_Wnarrowing,
>   		   "narrowing conversion of %qE from %qH to %qI",
>   		   init, ftype, type);
> diff --git a/gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.C b/gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.C
> new file mode 100644
> index 00000000000..048d484f46f
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.C
> @@ -0,0 +1,4 @@
> +// { dg-do compile { target c++14 } }
> +
> +#include "Wnarrowing2.h"
> +// { dg-error "narrowing conversion" "" { target *-*-* } 0 }
> diff --git a/gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.h b/gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.h
> new file mode 100644
> index 00000000000..7dafa51af14
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.h
> @@ -0,0 +1,2 @@
> +#pragma GCC system_header
> +constexpr unsigned f() { constexpr int n = -1; return unsigned{n}; }
> diff --git a/libstdc++-v3/testsuite/20_util/ratio/operations/ops_overflow_neg.cc b/libstdc++-v3/testsuite/20_util/ratio/operations/ops_overflow_neg.cc
> index 47d3c3a037e..f120e599a33 100644
> --- a/libstdc++-v3/testsuite/20_util/ratio/operations/ops_overflow_neg.cc
> +++ b/libstdc++-v3/testsuite/20_util/ratio/operations/ops_overflow_neg.cc
> @@ -39,6 +39,7 @@ test02()
>   }
>   
>   // { dg-error "required from here" "" { target *-*-* } 28 }
> +// { dg-error "expected initializer" "" { target *-*-* } 28 }
>   // { dg-error "expected initializer" "" { target *-*-* } 35 }
>   // { dg-error "expected initializer" "" { target *-*-* } 37 }
>   // { dg-error "overflow in addition" "" { target *-*-* } 0 }
> @@ -46,5 +47,6 @@ test02()
>   // { dg-error "overflow in multiplication" "" { target *-*-* } 100 }
>   // { dg-error "overflow in multiplication" "" { target *-*-* } 102 }
>   // { dg-error "overflow in constant expression" "" { target *-*-* } 0 }
> +// { dg-error "narrowing conversion" "" { target *-*-* } 0 }
>   // { dg-prune-output "out of range" }
>   // { dg-prune-output "not usable in a constant expression" }
> 
> base-commit: f364cdffa47af574f90f671b2dcf5afa91442741
>
diff mbox series

Patch

diff --git a/gcc/cp/typeck2.c b/gcc/cp/typeck2.c
index 6679e247816..dcfdff2f905 100644
--- a/gcc/cp/typeck2.c
+++ b/gcc/cp/typeck2.c
@@ -986,6 +986,7 @@  check_narrowing (tree type, tree init, tsubst_flags_t complain,
 	{
 	  int savederrorcount = errorcount;
 	  global_dc->pedantic_errors = 1;
+	  auto s = make_temp_override (global_dc->dc_warn_system_headers, true);
 	  pedwarn (loc, OPT_Wnarrowing,
 		   "narrowing conversion of %qE from %qH to %qI",
 		   init, ftype, type);
diff --git a/gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.C b/gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.C
new file mode 100644
index 00000000000..048d484f46f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.C
@@ -0,0 +1,4 @@ 
+// { dg-do compile { target c++14 } }
+
+#include "Wnarrowing2.h"
+// { dg-error "narrowing conversion" "" { target *-*-* } 0 }
diff --git a/gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.h b/gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.h
new file mode 100644
index 00000000000..7dafa51af14
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/Wnarrowing2.h
@@ -0,0 +1,2 @@ 
+#pragma GCC system_header
+constexpr unsigned f() { constexpr int n = -1; return unsigned{n}; }
diff --git a/libstdc++-v3/testsuite/20_util/ratio/operations/ops_overflow_neg.cc b/libstdc++-v3/testsuite/20_util/ratio/operations/ops_overflow_neg.cc
index 47d3c3a037e..f120e599a33 100644
--- a/libstdc++-v3/testsuite/20_util/ratio/operations/ops_overflow_neg.cc
+++ b/libstdc++-v3/testsuite/20_util/ratio/operations/ops_overflow_neg.cc
@@ -39,6 +39,7 @@  test02()
 }
 
 // { dg-error "required from here" "" { target *-*-* } 28 }
+// { dg-error "expected initializer" "" { target *-*-* } 28 }
 // { dg-error "expected initializer" "" { target *-*-* } 35 }
 // { dg-error "expected initializer" "" { target *-*-* } 37 }
 // { dg-error "overflow in addition" "" { target *-*-* } 0 }
@@ -46,5 +47,6 @@  test02()
 // { dg-error "overflow in multiplication" "" { target *-*-* } 100 }
 // { dg-error "overflow in multiplication" "" { target *-*-* } 102 }
 // { dg-error "overflow in constant expression" "" { target *-*-* } 0 }
+// { dg-error "narrowing conversion" "" { target *-*-* } 0 }
 // { dg-prune-output "out of range" }
 // { dg-prune-output "not usable in a constant expression" }