| Message ID | 20240801202038.3945271-1-polacek@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | c++: Move -Wdangling-reference to -Wextra | expand |
On 8/1/24 4:20 PM, Marek Polacek wrote: > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > -- >8 -- > Despite a number of mitigations (don't warn for std::span-like classes, > lambdas, adding [[gnu::no_dangling]], etc.), the warning still seems to > cause some grief. Let's move the warning to -Wextra, then. Any references to the grief? The patch is OK. > gcc/c-family/ChangeLog: > > * c.opt (Wdangling-reference): Move from -Wall to -Wextra. > > gcc/ChangeLog: > > * doc/invoke.texi: Document that -Wdangling-reference is > enabled by -Wextra. > --- > gcc/c-family/c.opt | 2 +- > gcc/doc/invoke.texi | 3 ++- > 2 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt > index a52682d835c..979f17a7e32 100644 > --- a/gcc/c-family/c.opt > +++ b/gcc/c-family/c.opt > @@ -604,7 +604,7 @@ C ObjC C++ ObjC++ Joined RejectNegative UInteger Var(warn_dangling_pointer) Warn > Warn for uses of pointers to auto variables whose lifetime has ended. > > Wdangling-reference > -C++ ObjC++ Var(warn_dangling_reference) Warning LangEnabledBy(C++ ObjC++, Wall) > +C++ ObjC++ Var(warn_dangling_reference) Warning LangEnabledBy(C++ ObjC++, Wextra) > Warn when a reference is bound to a temporary whose lifetime has ended. > > Wdate-time > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi > index ef2213b4e84..252b232e9f2 100644 > --- a/gcc/doc/invoke.texi > +++ b/gcc/doc/invoke.texi > @@ -3962,7 +3962,7 @@ that has a pointer data member and a trivial destructor. > The warning can be disabled by using the @code{gnu::no_dangling} attribute > (@pxref{C++ Attributes}). > > -This warning is enabled by @option{-Wall}. > +This warning is enabled by @option{-Wextra}. > > @opindex Wdelete-non-virtual-dtor > @opindex Wno-delete-non-virtual-dtor > @@ -6481,6 +6481,7 @@ name is still supported, but the newer name is more descriptive.) > -Wcalloc-transposed-args > -Wcast-function-type > -Wclobbered > +-Wdangling-reference @r{(C++ only)} > -Wdeprecated-copy @r{(C++ and Objective-C++ only)} > -Wempty-body > -Wenum-conversion @r{(only for C/ObjC)} > > base-commit: 32e678b2ed752154b2f96719e33f11a7c6417f20
On Thu, Aug 01, 2024 at 05:18:35PM -0400, Jason Merrill wrote: > On 8/1/24 4:20 PM, Marek Polacek wrote: > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > > > -- >8 -- > > Despite a number of mitigations (don't warn for std::span-like classes, > > lambdas, adding [[gnu::no_dangling]], etc.), the warning still seems to > > cause some grief. Let's move the warning to -Wextra, then. > > Any references to the grief? Two recent: https://gcc.gnu.org/PR115361 https://gcc.gnu.org/PR115730 > The patch is OK. Thanks. Marek
On Fri, 2 Aug 2024, Marek Polacek wrote: > On Thu, Aug 01, 2024 at 05:18:35PM -0400, Jason Merrill wrote: > > On 8/1/24 4:20 PM, Marek Polacek wrote: > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > > > > > -- >8 -- > > > Despite a number of mitigations (don't warn for std::span-like classes, > > > lambdas, adding [[gnu::no_dangling]], etc.), the warning still seems to > > > cause some grief. Let's move the warning to -Wextra, then. > > > > Any references to the grief? > > Two recent: > https://gcc.gnu.org/PR115361 > https://gcc.gnu.org/PR115730 FWIW PR115361 suggested adding another mitigation: Since the heuristic is concerned only with dangling references to *members of the GetKey object itself*, could you maybe add yet another heuristic to suppress the warning whenever the GetKey object is_empty? That seems sensible to me, and would also resolve PR115229. > > > The patch is OK. > > Thanks. > > Marek > >
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt index a52682d835c..979f17a7e32 100644 --- a/gcc/c-family/c.opt +++ b/gcc/c-family/c.opt @@ -604,7 +604,7 @@ C ObjC C++ ObjC++ Joined RejectNegative UInteger Var(warn_dangling_pointer) Warn Warn for uses of pointers to auto variables whose lifetime has ended. Wdangling-reference -C++ ObjC++ Var(warn_dangling_reference) Warning LangEnabledBy(C++ ObjC++, Wall) +C++ ObjC++ Var(warn_dangling_reference) Warning LangEnabledBy(C++ ObjC++, Wextra) Warn when a reference is bound to a temporary whose lifetime has ended. Wdate-time diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index ef2213b4e84..252b232e9f2 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -3962,7 +3962,7 @@ that has a pointer data member and a trivial destructor. The warning can be disabled by using the @code{gnu::no_dangling} attribute (@pxref{C++ Attributes}). -This warning is enabled by @option{-Wall}. +This warning is enabled by @option{-Wextra}. @opindex Wdelete-non-virtual-dtor @opindex Wno-delete-non-virtual-dtor @@ -6481,6 +6481,7 @@ name is still supported, but the newer name is more descriptive.) -Wcalloc-transposed-args -Wcast-function-type -Wclobbered +-Wdangling-reference @r{(C++ only)} -Wdeprecated-copy @r{(C++ and Objective-C++ only)} -Wempty-body -Wenum-conversion @r{(only for C/ObjC)}