Re: [PATCH] c++: Quash bogus -Wunused-value with new [PR107797]
On 1/23/23 16:28, Marek Polacek wrote: On Fri, Jan 20, 2023 at 02:37:19PM -0500, Jason Merrill wrote: On 1/19/23 21:03, Marek Polacek wrote: We shouldn't emit "right operand of comma operator has no effect" when that comma operator was created by the compiler for "new int{}". convert_to_void/COMPOUND_EXPR already checks warning_suppressed_p so we can just suppress -Wunused-value. Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? PR c++/107797 gcc/cp/ChangeLog: * cvt.cc (ocp_convert): copy_warning when creating a new COMPOUND_EXPR. * init.cc (build_new_1): Suppress -Wunused-value on compiler-generated COMPOUND_EXPRs. gcc/testsuite/ChangeLog: * g++.dg/warn/Wunused-value-1.C: New test. --- gcc/cp/cvt.cc | 6 -- gcc/cp/init.cc | 2 ++ gcc/testsuite/g++.dg/warn/Wunused-value-1.C | 12 3 files changed, 18 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/g++.dg/warn/Wunused-value-1.C diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc index f816c474cef..52e96fbe590 100644 --- a/gcc/cp/init.cc +++ b/gcc/cp/init.cc @@ -3800,6 +3800,8 @@ build_new_1 (vec **placement, tree type, tree nelts, if (cookie_expr) rval = build2 (COMPOUND_EXPR, TREE_TYPE (rval), cookie_expr, rval); + suppress_warning (rval, OPT_Wunused_value); This makes sense, but IIUC since rval is built with no location, this just sets nowarning_flag? Correct (I didn't realize this when writing the patch). There's another suppress_warning on a location-less expr just a few lines above. if (rval == data_addr && TREE_CODE (alloc_expr) == TARGET_EXPR) /* If we don't have an initializer or a cookie, strip the TARGET_EXPR and return the call (which doesn't need to be adjusted). */ diff --git a/gcc/cp/cvt.cc b/gcc/cp/cvt.cc index 0cbfd8060cb..17827d06a4a 100644 --- a/gcc/cp/cvt.cc +++ b/gcc/cp/cvt.cc @@ -711,8 +711,10 @@ ocp_convert (tree type, tree expr, int convtype, int flags, return error_mark_node; if (e == TREE_OPERAND (expr, 1)) return expr; - return build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR, TREE_TYPE (e), -TREE_OPERAND (expr, 0), e); + e = build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR, TREE_TYPE (e), + TREE_OPERAND (expr, 0), e); + copy_warning (e, expr); And so I don't know what effect this would have; copy_warning doesn't seem to propagate nowarning_flag, which seems like a bug. It actually does propagate nowarning_flag: in copy_warning we have 219 /* The no-warning bit might be set even if the map has not been consulted, or 220 otherwise if there's no entry in the map. */ 221 set_no_warning_bit (to, supp); so 'e' ends up with TREE_NO_WARNING set. Ah, yes. Pesky overloaded functions. I would not think we want to build 'rval' in build_new_1 with a location or use TREE_NO_WARNING directly instead of suppress_warning so I'm leaving the patch as-is, but please let me know if you disagree. Agreed, the patch is OK. Jason
Re: [PATCH] c++: Quash bogus -Wunused-value with new [PR107797]
On Fri, Jan 20, 2023 at 02:37:19PM -0500, Jason Merrill wrote: > On 1/19/23 21:03, Marek Polacek wrote: > > We shouldn't emit "right operand of comma operator has no effect" > > when that comma operator was created by the compiler for "new int{}". > > convert_to_void/COMPOUND_EXPR already checks warning_suppressed_p so > > we can just suppress -Wunused-value. > > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > > > PR c++/107797 > > > > gcc/cp/ChangeLog: > > > > * cvt.cc (ocp_convert): copy_warning when creating a new > > COMPOUND_EXPR. > > * init.cc (build_new_1): Suppress -Wunused-value on > > compiler-generated COMPOUND_EXPRs. > > > > gcc/testsuite/ChangeLog: > > > > * g++.dg/warn/Wunused-value-1.C: New test. > > --- > > gcc/cp/cvt.cc | 6 -- > > gcc/cp/init.cc | 2 ++ > > gcc/testsuite/g++.dg/warn/Wunused-value-1.C | 12 > > 3 files changed, 18 insertions(+), 2 deletions(-) > > create mode 100644 gcc/testsuite/g++.dg/warn/Wunused-value-1.C > > > > diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc > > index f816c474cef..52e96fbe590 100644 > > --- a/gcc/cp/init.cc > > +++ b/gcc/cp/init.cc > > @@ -3800,6 +3800,8 @@ build_new_1 (vec **placement, tree type, > > tree nelts, > > if (cookie_expr) > > rval = build2 (COMPOUND_EXPR, TREE_TYPE (rval), cookie_expr, rval); > > + suppress_warning (rval, OPT_Wunused_value); > > This makes sense, but IIUC since rval is built with no location, this just > sets nowarning_flag? Correct (I didn't realize this when writing the patch). There's another suppress_warning on a location-less expr just a few lines above. > > if (rval == data_addr && TREE_CODE (alloc_expr) == TARGET_EXPR) > > /* If we don't have an initializer or a cookie, strip the TARGET_EXPR > > and return the call (which doesn't need to be adjusted). */ > > diff --git a/gcc/cp/cvt.cc b/gcc/cp/cvt.cc > > index 0cbfd8060cb..17827d06a4a 100644 > > --- a/gcc/cp/cvt.cc > > +++ b/gcc/cp/cvt.cc > > @@ -711,8 +711,10 @@ ocp_convert (tree type, tree expr, int convtype, int > > flags, > > return error_mark_node; > >if (e == TREE_OPERAND (expr, 1)) > > return expr; > > - return build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR, TREE_TYPE > > (e), > > -TREE_OPERAND (expr, 0), e); > > + e = build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR, TREE_TYPE (e), > > + TREE_OPERAND (expr, 0), e); > > + copy_warning (e, expr); > > And so I don't know what effect this would have; copy_warning doesn't seem > to propagate nowarning_flag, which seems like a bug. It actually does propagate nowarning_flag: in copy_warning we have 219 /* The no-warning bit might be set even if the map has not been consulted, or 220 otherwise if there's no entry in the map. */ 221 set_no_warning_bit (to, supp); so 'e' ends up with TREE_NO_WARNING set. I would not think we want to build 'rval' in build_new_1 with a location or use TREE_NO_WARNING directly instead of suppress_warning so I'm leaving the patch as-is, but please let me know if you disagree. Marek
Re: [PATCH] c++: Quash bogus -Wunused-value with new [PR107797]
On 1/19/23 21:03, Marek Polacek wrote: We shouldn't emit "right operand of comma operator has no effect" when that comma operator was created by the compiler for "new int{}". convert_to_void/COMPOUND_EXPR already checks warning_suppressed_p so we can just suppress -Wunused-value. Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? PR c++/107797 gcc/cp/ChangeLog: * cvt.cc (ocp_convert): copy_warning when creating a new COMPOUND_EXPR. * init.cc (build_new_1): Suppress -Wunused-value on compiler-generated COMPOUND_EXPRs. gcc/testsuite/ChangeLog: * g++.dg/warn/Wunused-value-1.C: New test. --- gcc/cp/cvt.cc | 6 -- gcc/cp/init.cc | 2 ++ gcc/testsuite/g++.dg/warn/Wunused-value-1.C | 12 3 files changed, 18 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/g++.dg/warn/Wunused-value-1.C diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc index f816c474cef..52e96fbe590 100644 --- a/gcc/cp/init.cc +++ b/gcc/cp/init.cc @@ -3800,6 +3800,8 @@ build_new_1 (vec **placement, tree type, tree nelts, if (cookie_expr) rval = build2 (COMPOUND_EXPR, TREE_TYPE (rval), cookie_expr, rval); + suppress_warning (rval, OPT_Wunused_value); This makes sense, but IIUC since rval is built with no location, this just sets nowarning_flag? if (rval == data_addr && TREE_CODE (alloc_expr) == TARGET_EXPR) /* If we don't have an initializer or a cookie, strip the TARGET_EXPR and return the call (which doesn't need to be adjusted). */ diff --git a/gcc/cp/cvt.cc b/gcc/cp/cvt.cc index 0cbfd8060cb..17827d06a4a 100644 --- a/gcc/cp/cvt.cc +++ b/gcc/cp/cvt.cc @@ -711,8 +711,10 @@ ocp_convert (tree type, tree expr, int convtype, int flags, return error_mark_node; if (e == TREE_OPERAND (expr, 1)) return expr; - return build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR, TREE_TYPE (e), -TREE_OPERAND (expr, 0), e); + e = build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR, TREE_TYPE (e), + TREE_OPERAND (expr, 0), e); + copy_warning (e, expr); And so I don't know what effect this would have; copy_warning doesn't seem to propagate nowarning_flag, which seems like a bug. + return e; } complete_type (type); diff --git a/gcc/testsuite/g++.dg/warn/Wunused-value-1.C b/gcc/testsuite/g++.dg/warn/Wunused-value-1.C new file mode 100644 index 000..2ba5587fce0 --- /dev/null +++ b/gcc/testsuite/g++.dg/warn/Wunused-value-1.C @@ -0,0 +1,12 @@ +// PR c++/107797 +// { dg-do compile { target c++11 } } +// { dg-options "-Wunused" } + +void +g () +{ + (long) new int{}; + long(new int{}); + (long) new int(); + long(new int()); +} base-commit: 86caab6c5d1e26e1c54c3dceacc873d6e27bfc09
[PATCH] c++: Quash bogus -Wunused-value with new [PR107797]
We shouldn't emit "right operand of comma operator has no effect" when that comma operator was created by the compiler for "new int{}". convert_to_void/COMPOUND_EXPR already checks warning_suppressed_p so we can just suppress -Wunused-value. Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? PR c++/107797 gcc/cp/ChangeLog: * cvt.cc (ocp_convert): copy_warning when creating a new COMPOUND_EXPR. * init.cc (build_new_1): Suppress -Wunused-value on compiler-generated COMPOUND_EXPRs. gcc/testsuite/ChangeLog: * g++.dg/warn/Wunused-value-1.C: New test. --- gcc/cp/cvt.cc | 6 -- gcc/cp/init.cc | 2 ++ gcc/testsuite/g++.dg/warn/Wunused-value-1.C | 12 3 files changed, 18 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/g++.dg/warn/Wunused-value-1.C diff --git a/gcc/cp/cvt.cc b/gcc/cp/cvt.cc index 0cbfd8060cb..17827d06a4a 100644 --- a/gcc/cp/cvt.cc +++ b/gcc/cp/cvt.cc @@ -711,8 +711,10 @@ ocp_convert (tree type, tree expr, int convtype, int flags, return error_mark_node; if (e == TREE_OPERAND (expr, 1)) return expr; - return build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR, TREE_TYPE (e), -TREE_OPERAND (expr, 0), e); + e = build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR, TREE_TYPE (e), + TREE_OPERAND (expr, 0), e); + copy_warning (e, expr); + return e; } complete_type (type); diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc index f816c474cef..52e96fbe590 100644 --- a/gcc/cp/init.cc +++ b/gcc/cp/init.cc @@ -3800,6 +3800,8 @@ build_new_1 (vec **placement, tree type, tree nelts, if (cookie_expr) rval = build2 (COMPOUND_EXPR, TREE_TYPE (rval), cookie_expr, rval); + suppress_warning (rval, OPT_Wunused_value); + if (rval == data_addr && TREE_CODE (alloc_expr) == TARGET_EXPR) /* If we don't have an initializer or a cookie, strip the TARGET_EXPR and return the call (which doesn't need to be adjusted). */ diff --git a/gcc/testsuite/g++.dg/warn/Wunused-value-1.C b/gcc/testsuite/g++.dg/warn/Wunused-value-1.C new file mode 100644 index 000..2ba5587fce0 --- /dev/null +++ b/gcc/testsuite/g++.dg/warn/Wunused-value-1.C @@ -0,0 +1,12 @@ +// PR c++/107797 +// { dg-do compile { target c++11 } } +// { dg-options "-Wunused" } + +void +g () +{ + (long) new int{}; + long(new int{}); + (long) new int(); + long(new int()); +} base-commit: 86caab6c5d1e26e1c54c3dceacc873d6e27bfc09 -- 2.39.0