| Message ID | YjIWdn9rM+s9h2BJ@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | c++, v2: Fix up constexpr evaluation of new with zero sized types [PR104568] | expand |
On 3/16/22 12:55, Jakub Jelinek wrote: > On Tue, Mar 15, 2022 at 04:19:05PM -0400, Jason Merrill wrote: >>> But if you strongly prefer it that way, I can do that. >>> Note, probably not 3 new args but 4, depends on whether we could turn >>> all those cases where the tree arg0 = CALL_EXPR_ARG (oldop, 0); >>> is done but var_size_adjusted is false into assertion failures. >>> I'm worried that with the zero size of element we could end up with >>> a variable number of elements which when multiplied by 0 gives constant 0, >>> though hopefully that would be rejected earlier during constant evaluation. >> >> Or we could move all the adjustment into a separate function and only ever >> pass the number of elements to build_new_constexpr_heap_type? > > So like this? > > 2022-03-16 Jakub Jelinek <jakub@redhat.com> > > PR c++/104568 > * init.cc (build_new_constexpr_heap_type): Remove FULL_SIZE > argument and its handling, instead add ITYPE2 argument. Only > support COOKIE_SIZE != NULL. > (build_new_1): If size is 0, change it to 0 * outer_nelts if > outer_nelts is non-NULL. Pass type rather than elt_type to > maybe_wrap_new_for_constexpr. > * constexpr.cc (build_new_constexpr_heap_type): New function. > (cxx_eval_constant_expression) <case CONVERT_EXPR>: > If elt_size is zero sized type, try to recover outer_nelts from > the size argument to operator new/new[] and pass that as > arg_size to build_new_constexpr_heap_type. Pass ctx, > non_constant_p and overflow_p to that call too. > > * g++.dg/cpp2a/constexpr-new22.C: New test. > > --- gcc/cp/constexpr.cc.jj 2022-03-16 15:25:26.294551244 +0100 > +++ gcc/cp/constexpr.cc 2022-03-16 17:27:08.202184961 +0100 > @@ -6422,6 +6422,84 @@ maybe_warn_about_constant_value (locatio > } > } > > +/* For element type ELT_TYPE, return the appropriate type of the heap object > + containing such element(s). COOKIE_SIZE is NULL or the size of cookie > + in bytes. If COOKIE_SIZE is NULL, return array type > + ELT_TYPE[FULL_SIZE / sizeof(ELT_TYPE)], otherwise return > + struct { size_t[COOKIE_SIZE/sizeof(size_t)]; ELT_TYPE[N]; } > + where N is is computed such that the size of the struct fits into FULL_SIZE. > + If ARG_SIZE is non-NULL, it is the first argument to the new operator. > + It should be passed if ELT_TYPE is zero sized type in which case FULL_SIZE > + will be also 0 and so it is not possible to determine the actual array > + size. CTX, NON_CONSTANT_P and OVERFLOW_P are used during constant > + expression evaluation of subexpressions of ARG_SIZE. */ > + > +tree Let's make this static. > +build_new_constexpr_heap_type (const constexpr_ctx *ctx, tree elt_type, > + tree cookie_size, tree full_size, tree arg_size, > + bool *non_constant_p, bool *overflow_p) > +{ > + gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size)); > + gcc_assert (tree_fits_uhwi_p (full_size)); > + unsigned HOST_WIDE_INT csz = cookie_size ? tree_to_uhwi (cookie_size) : 0; > + if (arg_size) > + { > + STRIP_NOPS (arg_size); > + if (cookie_size) > + { > + if (TREE_CODE (arg_size) != PLUS_EXPR) > + arg_size = NULL_TREE; > + else if (TREE_CODE (TREE_OPERAND (arg_size, 0)) == INTEGER_CST > + && tree_int_cst_equal (cookie_size, > + TREE_OPERAND (arg_size, 0))) > + { > + arg_size = TREE_OPERAND (arg_size, 1); > + STRIP_NOPS (arg_size); > + } > + else if (TREE_CODE (TREE_OPERAND (arg_size, 1)) == INTEGER_CST > + && tree_int_cst_equal (cookie_size, > + TREE_OPERAND (arg_size, 1))) > + { > + arg_size = TREE_OPERAND (arg_size, 0); > + STRIP_NOPS (arg_size); > + } > + else > + arg_size = NULL_TREE; > + } > + if (arg_size && TREE_CODE (arg_size) == MULT_EXPR) > + { > + tree op0 = TREE_OPERAND (arg_size, 0); > + tree op1 = TREE_OPERAND (arg_size, 1); > + if (integer_zerop (op0)) > + arg_size > + = cxx_eval_constant_expression (ctx, op1, false, non_constant_p, > + overflow_p); > + else if (integer_zerop (op1)) > + arg_size > + = cxx_eval_constant_expression (ctx, op0, false, non_constant_p, > + overflow_p); > + else > + arg_size = NULL_TREE; > + } > + else > + arg_size = NULL_TREE; > + } > + > + unsigned HOST_WIDE_INT fsz = tree_to_uhwi (arg_size ? arg_size : full_size); > + unsigned HOST_WIDE_INT esz = int_size_in_bytes (elt_type); esz could move inside the if. OK with those changes, thanks. > + if (!arg_size) > + { > + gcc_assert (fsz >= csz); > + fsz -= csz; > + if (esz) > + fsz /= esz; > + } > + tree itype2 = build_index_type (size_int (fsz - 1)); > + if (!cookie_size) > + return build_cplus_array_type (elt_type, itype2); > + return build_new_constexpr_heap_type (elt_type, cookie_size, itype2); > +} > + > /* Attempt to reduce the expression T to a constant value. > On failure, issue diagnostic and return error_mark_node. */ > /* FIXME unify with c_fully_fold */ > @@ -7253,6 +7331,7 @@ cxx_eval_constant_expression (const cons > tree var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); > tree elt_type = TREE_TYPE (type); > tree cookie_size = NULL_TREE; > + tree arg_size = NULL_TREE; > if (TREE_CODE (elt_type) == RECORD_TYPE > && TYPE_NAME (elt_type) == heap_identifier) > { > @@ -7264,9 +7343,21 @@ cxx_eval_constant_expression (const cons > DECL_NAME (var) > = (DECL_NAME (var) == heap_uninit_identifier > ? heap_identifier : heap_vec_identifier); > + /* For zero sized elt_type, try to recover how many outer_nelts > + it should have. */ > + if ((cookie_size ? tree_int_cst_equal (var_size, cookie_size) > + : integer_zerop (var_size)) > + && !int_size_in_bytes (elt_type) > + && TREE_CODE (oldop) == CALL_EXPR > + && call_expr_nargs (oldop) >= 1) > + if (tree fun = get_function_named_in_call (oldop)) > + if (cxx_replaceable_global_alloc_fn (fun) > + && IDENTIFIER_NEW_OP_P (DECL_NAME (fun))) > + arg_size = CALL_EXPR_ARG (oldop, 0); > TREE_TYPE (var) > - = build_new_constexpr_heap_type (elt_type, cookie_size, > - var_size); > + = build_new_constexpr_heap_type (ctx, elt_type, cookie_size, > + var_size, arg_size, > + non_constant_p, overflow_p); > TREE_TYPE (TREE_OPERAND (op, 0)) > = build_pointer_type (TREE_TYPE (var)); > } > --- gcc/cp/init.cc.jj 2022-03-16 15:25:26.431549398 +0100 > +++ gcc/cp/init.cc 2022-03-16 17:23:03.922500101 +0100 > @@ -2931,33 +2931,17 @@ std_placement_new_fn_p (tree alloc_fn) > } > > /* For element type ELT_TYPE, return the appropriate type of the heap object > - containing such element(s). COOKIE_SIZE is NULL or the size of cookie > - in bytes. FULL_SIZE is NULL if it is unknown how big the heap allocation > - will be, otherwise size of the heap object. If COOKIE_SIZE is NULL, > - return array type ELT_TYPE[FULL_SIZE / sizeof(ELT_TYPE)], otherwise return > + containing such element(s). COOKIE_SIZE is the size of cookie in bytes. > + Return > struct { size_t[COOKIE_SIZE/sizeof(size_t)]; ELT_TYPE[N]; } > - where N is nothing (flexible array member) if FULL_SIZE is NULL, otherwise > - it is computed such that the size of the struct fits into FULL_SIZE. */ > + where N is nothing (flexible array member) if ITYPE2 is NULL, otherwise > + the array has ITYPE2 as its TYPE_DOMAIN. */ > > tree > -build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree full_size) > +build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree itype2) > { > - gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size)); > - gcc_assert (full_size == NULL_TREE || tree_fits_uhwi_p (full_size)); > - unsigned HOST_WIDE_INT csz = cookie_size ? tree_to_uhwi (cookie_size) : 0; > - tree itype2 = NULL_TREE; > - if (full_size) > - { > - unsigned HOST_WIDE_INT fsz = tree_to_uhwi (full_size); > - gcc_assert (fsz >= csz); > - fsz -= csz; > - fsz /= int_size_in_bytes (elt_type); > - itype2 = build_index_type (size_int (fsz - 1)); > - if (!cookie_size) > - return build_cplus_array_type (elt_type, itype2); > - } > - else > - gcc_assert (cookie_size); > + gcc_assert (tree_fits_uhwi_p (cookie_size)); > + unsigned HOST_WIDE_INT csz = tree_to_uhwi (cookie_size); > csz /= int_size_in_bytes (sizetype); > tree itype1 = build_index_type (size_int (csz - 1)); > tree atype1 = build_cplus_array_type (sizetype, itype1); > @@ -3408,6 +3392,12 @@ build_new_1 (vec<tree, va_gc> **placemen > outer_nelts_check = NULL_TREE; > } > > + /* If size is zero e.g. due to type having zero size, try to > + preserve outer_nelts for constant expression evaluation > + purposes. */ > + if (integer_zerop (size) && outer_nelts) > + size = build2 (MULT_EXPR, TREE_TYPE (size), size, outer_nelts); > + > alloc_call = build_operator_new_call (fnname, placement, > &size, &cookie_size, > align_arg, outer_nelts_check, > @@ -3484,7 +3474,7 @@ build_new_1 (vec<tree, va_gc> **placemen > } > > if (cookie_size) > - alloc_call = maybe_wrap_new_for_constexpr (alloc_call, elt_type, > + alloc_call = maybe_wrap_new_for_constexpr (alloc_call, type, > cookie_size); > > /* In the simple case, we can stop now. */ > --- gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C.jj 2022-03-16 16:45:04.011372629 +0100 > +++ gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C 2022-03-16 16:45:04.011372629 +0100 > @@ -0,0 +1,42 @@ > +// PR c++/104568 > +// { dg-do compile { target c++20 } } > +// { dg-options "" } > + > +struct S { int s; constexpr S () : s (0) {} constexpr ~S () {} }; > +typedef int T[0]; > +typedef int U[0]; > + > +constexpr bool > +foo () > +{ > + auto p = new T[2]; > + auto q1 = &p[0]; > + auto q2 = &p[1]; > + auto q3 = &p[2]; > + delete[] p; > + return true; > +} > + > +constexpr bool > +bar () > +{ > + auto p = new U[2]; > + auto q1 = &p[0]; > + auto q2 = &p[1]; > + auto q3 = &p[2]; > + delete[] p; > + return true; > +} > + > +constexpr bool > +baz () > +{ > + auto p = new T[0]; > + auto q1 = &p[0]; > + delete[] p; > + return true; > +} > + > +constexpr bool a = foo (); > +constexpr bool b = bar (); > +constexpr bool c = baz (); > > > Jakub >
--- gcc/cp/constexpr.cc.jj 2022-03-16 15:25:26.294551244 +0100 +++ gcc/cp/constexpr.cc 2022-03-16 17:27:08.202184961 +0100 @@ -6422,6 +6422,84 @@ maybe_warn_about_constant_value (locatio } } +/* For element type ELT_TYPE, return the appropriate type of the heap object + containing such element(s). COOKIE_SIZE is NULL or the size of cookie + in bytes. If COOKIE_SIZE is NULL, return array type + ELT_TYPE[FULL_SIZE / sizeof(ELT_TYPE)], otherwise return + struct { size_t[COOKIE_SIZE/sizeof(size_t)]; ELT_TYPE[N]; } + where N is is computed such that the size of the struct fits into FULL_SIZE. + If ARG_SIZE is non-NULL, it is the first argument to the new operator. + It should be passed if ELT_TYPE is zero sized type in which case FULL_SIZE + will be also 0 and so it is not possible to determine the actual array + size. CTX, NON_CONSTANT_P and OVERFLOW_P are used during constant + expression evaluation of subexpressions of ARG_SIZE. */ + +tree +build_new_constexpr_heap_type (const constexpr_ctx *ctx, tree elt_type, + tree cookie_size, tree full_size, tree arg_size, + bool *non_constant_p, bool *overflow_p) +{ + gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size)); + gcc_assert (tree_fits_uhwi_p (full_size)); + unsigned HOST_WIDE_INT csz = cookie_size ? tree_to_uhwi (cookie_size) : 0; + if (arg_size) + { + STRIP_NOPS (arg_size); + if (cookie_size) + { + if (TREE_CODE (arg_size) != PLUS_EXPR) + arg_size = NULL_TREE; + else if (TREE_CODE (TREE_OPERAND (arg_size, 0)) == INTEGER_CST + && tree_int_cst_equal (cookie_size, + TREE_OPERAND (arg_size, 0))) + { + arg_size = TREE_OPERAND (arg_size, 1); + STRIP_NOPS (arg_size); + } + else if (TREE_CODE (TREE_OPERAND (arg_size, 1)) == INTEGER_CST + && tree_int_cst_equal (cookie_size, + TREE_OPERAND (arg_size, 1))) + { + arg_size = TREE_OPERAND (arg_size, 0); + STRIP_NOPS (arg_size); + } + else + arg_size = NULL_TREE; + } + if (arg_size && TREE_CODE (arg_size) == MULT_EXPR) + { + tree op0 = TREE_OPERAND (arg_size, 0); + tree op1 = TREE_OPERAND (arg_size, 1); + if (integer_zerop (op0)) + arg_size + = cxx_eval_constant_expression (ctx, op1, false, non_constant_p, + overflow_p); + else if (integer_zerop (op1)) + arg_size + = cxx_eval_constant_expression (ctx, op0, false, non_constant_p, + overflow_p); + else + arg_size = NULL_TREE; + } + else + arg_size = NULL_TREE; + } + + unsigned HOST_WIDE_INT fsz = tree_to_uhwi (arg_size ? arg_size : full_size); + unsigned HOST_WIDE_INT esz = int_size_in_bytes (elt_type); + if (!arg_size) + { + gcc_assert (fsz >= csz); + fsz -= csz; + if (esz) + fsz /= esz; + } + tree itype2 = build_index_type (size_int (fsz - 1)); + if (!cookie_size) + return build_cplus_array_type (elt_type, itype2); + return build_new_constexpr_heap_type (elt_type, cookie_size, itype2); +} + /* Attempt to reduce the expression T to a constant value. On failure, issue diagnostic and return error_mark_node. */ /* FIXME unify with c_fully_fold */ @@ -7253,6 +7331,7 @@ cxx_eval_constant_expression (const cons tree var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); tree elt_type = TREE_TYPE (type); tree cookie_size = NULL_TREE; + tree arg_size = NULL_TREE; if (TREE_CODE (elt_type) == RECORD_TYPE && TYPE_NAME (elt_type) == heap_identifier) { @@ -7264,9 +7343,21 @@ cxx_eval_constant_expression (const cons DECL_NAME (var) = (DECL_NAME (var) == heap_uninit_identifier ? heap_identifier : heap_vec_identifier); + /* For zero sized elt_type, try to recover how many outer_nelts + it should have. */ + if ((cookie_size ? tree_int_cst_equal (var_size, cookie_size) + : integer_zerop (var_size)) + && !int_size_in_bytes (elt_type) + && TREE_CODE (oldop) == CALL_EXPR + && call_expr_nargs (oldop) >= 1) + if (tree fun = get_function_named_in_call (oldop)) + if (cxx_replaceable_global_alloc_fn (fun) + && IDENTIFIER_NEW_OP_P (DECL_NAME (fun))) + arg_size = CALL_EXPR_ARG (oldop, 0); TREE_TYPE (var) - = build_new_constexpr_heap_type (elt_type, cookie_size, - var_size); + = build_new_constexpr_heap_type (ctx, elt_type, cookie_size, + var_size, arg_size, + non_constant_p, overflow_p); TREE_TYPE (TREE_OPERAND (op, 0)) = build_pointer_type (TREE_TYPE (var)); } --- gcc/cp/init.cc.jj 2022-03-16 15:25:26.431549398 +0100 +++ gcc/cp/init.cc 2022-03-16 17:23:03.922500101 +0100 @@ -2931,33 +2931,17 @@ std_placement_new_fn_p (tree alloc_fn) } /* For element type ELT_TYPE, return the appropriate type of the heap object - containing such element(s). COOKIE_SIZE is NULL or the size of cookie - in bytes. FULL_SIZE is NULL if it is unknown how big the heap allocation - will be, otherwise size of the heap object. If COOKIE_SIZE is NULL, - return array type ELT_TYPE[FULL_SIZE / sizeof(ELT_TYPE)], otherwise return + containing such element(s). COOKIE_SIZE is the size of cookie in bytes. + Return struct { size_t[COOKIE_SIZE/sizeof(size_t)]; ELT_TYPE[N]; } - where N is nothing (flexible array member) if FULL_SIZE is NULL, otherwise - it is computed such that the size of the struct fits into FULL_SIZE. */ + where N is nothing (flexible array member) if ITYPE2 is NULL, otherwise + the array has ITYPE2 as its TYPE_DOMAIN. */ tree -build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree full_size) +build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree itype2) { - gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size)); - gcc_assert (full_size == NULL_TREE || tree_fits_uhwi_p (full_size)); - unsigned HOST_WIDE_INT csz = cookie_size ? tree_to_uhwi (cookie_size) : 0; - tree itype2 = NULL_TREE; - if (full_size) - { - unsigned HOST_WIDE_INT fsz = tree_to_uhwi (full_size); - gcc_assert (fsz >= csz); - fsz -= csz; - fsz /= int_size_in_bytes (elt_type); - itype2 = build_index_type (size_int (fsz - 1)); - if (!cookie_size) - return build_cplus_array_type (elt_type, itype2); - } - else - gcc_assert (cookie_size); + gcc_assert (tree_fits_uhwi_p (cookie_size)); + unsigned HOST_WIDE_INT csz = tree_to_uhwi (cookie_size); csz /= int_size_in_bytes (sizetype); tree itype1 = build_index_type (size_int (csz - 1)); tree atype1 = build_cplus_array_type (sizetype, itype1); @@ -3408,6 +3392,12 @@ build_new_1 (vec<tree, va_gc> **placemen outer_nelts_check = NULL_TREE; } + /* If size is zero e.g. due to type having zero size, try to + preserve outer_nelts for constant expression evaluation + purposes. */ + if (integer_zerop (size) && outer_nelts) + size = build2 (MULT_EXPR, TREE_TYPE (size), size, outer_nelts); + alloc_call = build_operator_new_call (fnname, placement, &size, &cookie_size, align_arg, outer_nelts_check, @@ -3484,7 +3474,7 @@ build_new_1 (vec<tree, va_gc> **placemen } if (cookie_size) - alloc_call = maybe_wrap_new_for_constexpr (alloc_call, elt_type, + alloc_call = maybe_wrap_new_for_constexpr (alloc_call, type, cookie_size); /* In the simple case, we can stop now. */ --- gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C.jj 2022-03-16 16:45:04.011372629 +0100 +++ gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C 2022-03-16 16:45:04.011372629 +0100 @@ -0,0 +1,42 @@ +// PR c++/104568 +// { dg-do compile { target c++20 } } +// { dg-options "" } + +struct S { int s; constexpr S () : s (0) {} constexpr ~S () {} }; +typedef int T[0]; +typedef int U[0]; + +constexpr bool +foo () +{ + auto p = new T[2]; + auto q1 = &p[0]; + auto q2 = &p[1]; + auto q3 = &p[2]; + delete[] p; + return true; +} + +constexpr bool +bar () +{ + auto p = new U[2]; + auto q1 = &p[0]; + auto q2 = &p[1]; + auto q3 = &p[2]; + delete[] p; + return true; +} + +constexpr bool +baz () +{ + auto p = new T[0]; + auto q1 = &p[0]; + delete[] p; + return true; +} + +constexpr bool a = foo (); +constexpr bool b = bar (); +constexpr bool c = baz ();