On Mon, Jul 18, 2016 at 02:07:50PM -0400, Jason Merrill wrote: > On Mon, Jul 18, 2016 at 2:03 PM, Jakub Jelinek <ja...@redhat.com> wrote: > > On Mon, Jul 18, 2016 at 01:16:26PM -0400, Jason Merrill wrote: > > That is reasonable, but not 100% sure what to do if it returns NULL > > - it should return t, but if I do VERIFY_CONSTANT (t); there or > > manually > > if (!*non_constant_p) > > { > > if (!allow_non_constant) > > error ("%q+E is not a constant expression", t); > > *non_constant_p = true; > > } > > return t; > > it will print the original expression (without folded arguments). > > Another option would be to build_call_array_loc if we want to emit > > the error. Preferences? > > Hmm, I guess let's build the call for the error.
Ok. > > /* Fold away the NOP_EXPR from fold_builtin_n. */ > > new_call = fold (new_call); > > force_folding_builtin_constant_p = save_ffbcp; > > + > > + /* Folding some math builtins produces e.g. COMPOUND_EXPR etc. */ > > + if (cxx_dialect >= cxx14) > > + return cxx_eval_constant_expression (&new_ctx, new_call, lval, > > + non_constant_p, overflow_p); > > If we do this unconditionally, can we drop the fold above? So I've tried following patch, but on extern "C" double frexp (double, int *); struct S { #ifdef FREXP constexpr S (double a) : y {}, x (frexp (a, &y)) {} #else constexpr S (double a) : y {}, x ((y = 1, 0.8125)) {} #endif double x; int y; }; static_assert (S (6.5).x == 0.8125, ""); it means the testcase is accepted with -DFREXP in both -std=gnu++11 and -std=gnu++14 modes and without -DFREXP in -std=gnu++14 mode only. I can move over the fold call to the cxx11 block, but I think we need to reject it for C++11. 2016-07-18 Jakub Jelinek <ja...@redhat.com> PR c++/50060 * constexpr.c (cxx_eval_builtin_function_call): Pass false as lval when evaluating call arguments. Use fold_builtin_call_array instead of fold_build_call_array_loc, return t if it returns NULL. For C++14 and later, pass new_call to if new_call cxx_eval_constant_expression. * g++.dg/cpp1y/constexpr-50060.C: New test. --- gcc/cp/constexpr.c.jj 2016-07-16 10:41:04.525652516 +0200 +++ gcc/cp/constexpr.c 2016-07-18 20:18:08.035709874 +0200 @@ -1105,7 +1105,7 @@ cxx_eval_builtin_function_call (const co for (i = 0; i < nargs; ++i) { args[i] = cxx_eval_constant_expression (&new_ctx, CALL_EXPR_ARG (t, i), - lval, &dummy1, &dummy2); + false, &dummy1, &dummy2); if (bi_const_p) /* For __built_in_constant_p, fold all expressions with constant values even if they aren't C++ constant-expressions. */ @@ -1114,13 +1114,23 @@ cxx_eval_builtin_function_call (const co bool save_ffbcp = force_folding_builtin_constant_p; force_folding_builtin_constant_p = true; - new_call = fold_build_call_array_loc (EXPR_LOCATION (t), TREE_TYPE (t), - CALL_EXPR_FN (t), nargs, args); - /* Fold away the NOP_EXPR from fold_builtin_n. */ - new_call = fold (new_call); + new_call = fold_builtin_call_array (EXPR_LOCATION (t), TREE_TYPE (t), + CALL_EXPR_FN (t), nargs, args); force_folding_builtin_constant_p = save_ffbcp; - VERIFY_CONSTANT (new_call); - return new_call; + if (new_call == NULL) + { + if (!*non_constant_p && !ctx->quiet) + { + new_call = build_call_array_loc (EXPR_LOCATION (t), TREE_TYPE (t), + CALL_EXPR_FN (t), nargs, args); + error ("%q+E is not a constant expression", new_call); + } + *non_constant_p = true; + return t; + } + + return cxx_eval_constant_expression (&new_ctx, new_call, lval, + non_constant_p, overflow_p); } /* TEMP is the constant value of a temporary object of type TYPE. Adjust --- gcc/testsuite/g++.dg/cpp1y/constexpr-50060.C.jj 2016-07-18 19:45:30.528496123 +0200 +++ gcc/testsuite/g++.dg/cpp1y/constexpr-50060.C 2016-07-18 19:45:30.528496123 +0200 @@ -0,0 +1,100 @@ +// PR c++/50060 +// { dg-do compile { target c++14 } } + +// sincos and lgamma_r aren't available in -std=c++14, +// only in -std=gnu++14. Use __builtin_* in that case. +extern "C" void sincos (double, double *, double *); +extern "C" double frexp (double, int *); +extern "C" double modf (double, double *); +extern "C" double remquo (double, double, int *); +extern "C" double lgamma_r (double, int *); + +constexpr double +f0 (double x) +{ + double y {}; + double z {}; + __builtin_sincos (x, &y, &z); + return y; +} + +constexpr double +f1 (double x) +{ + double y {}; + double z {}; + __builtin_sincos (x, &y, &z); + return z; +} + +constexpr double +f2 (double x) +{ + int y {}; + return frexp (x, &y); +} + +constexpr int +f3 (double x) +{ + int y {}; + frexp (x, &y); + return y; +} + +constexpr double +f4 (double x) +{ + double y {}; + return modf (x, &y); +} + +constexpr double +f5 (double x) +{ + double y {}; + modf (x, &y); + return y; +} + +constexpr double +f6 (double x, double y) +{ + int z {}; + return remquo (x, y, &z); +} + +constexpr int +f7 (double x, double y) +{ + int z {}; + remquo (x, y, &z); + return z; +} + +constexpr double +f8 (double x) +{ + int y {}; + return __builtin_lgamma_r (x, &y); +} + +constexpr int +f9 (double x) +{ + int y {}; + __builtin_lgamma_r (x, &y); + return y; +} + +static_assert (f0 (0.0) == 0.0, ""); +static_assert (f1 (0.0) == 1.0, ""); +static_assert (f2 (6.5) == 0.8125, ""); +static_assert (f3 (6.5) == 3, ""); +static_assert (f4 (-7.25) == -0.25, ""); +static_assert (f5 (-7.25) == -7.0, ""); +static_assert (f6 (3.0, 2.0) == -1.0, ""); +static_assert (f7 (3.0, 2.0) == 2, ""); +static_assert (f8 (0.75) >= 0.20 && f8 (0.75) <= 0.21, ""); +static_assert (f8 (0.75) >= 0.20 && f8 (0.75) <= 0.21, ""); +static_assert (f9 (0.75) == 1, ""); Jakub