On 7/15/21 8:03 PM, Marek Polacek wrote:
Jonathan pointed me at this issue whereconstexpr 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
