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From: Marek Polacek <mpolacek@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-8336] c++: ICE with reinterpret_cast and switch [PR113545] Date: Fri, 16 Feb 2024 17:30:08 +0000 (GMT) [thread overview] Message-ID: <20240216173008.83CBB385800C@sourceware.org> (raw) https://gcc.gnu.org/g:e501a279fb4298c9b23637d573287e059b3b06c8 commit r13-8336-ge501a279fb4298c9b23637d573287e059b3b06c8 Author: Marek Polacek <polacek@redhat.com> Date: Fri Feb 16 12:25:26 2024 -0500 c++: ICE with reinterpret_cast and switch [PR113545] Jason, this is the patch you proposed for PR113545. It looks very safe so I'm posting it here so that it's not forgotten. PR c++/113545 gcc/cp/ChangeLog: * constexpr.cc (cxx_eval_switch_expr): If the condition doesn't reduce to an INTEGER_CST, consider it non-constant. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/constexpr-reinterpret3.C: New test. * g++.dg/cpp1y/constexpr-reinterpret4.C: New test. (cherry picked from commit 39d989022dd0eacf1a7b95b7b20621acbe717d70) Diff: --- gcc/cp/constexpr.cc | 10 ++++ .../g++.dg/cpp1y/constexpr-reinterpret3.C | 54 ++++++++++++++++++++++ .../g++.dg/cpp1y/constexpr-reinterpret4.C | 54 ++++++++++++++++++++++ 3 files changed, 118 insertions(+) diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index ab129c087555..a3c21e88e7ba 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -6722,6 +6722,16 @@ cxx_eval_switch_expr (const constexpr_ctx *ctx, tree t, cond = cxx_eval_constant_expression (ctx, cond, vc_prvalue, non_constant_p, overflow_p); VERIFY_CONSTANT (cond); + if (TREE_CODE (cond) != INTEGER_CST) + { + /* If the condition doesn't reduce to an INTEGER_CST it isn't a usable + switch condition even if it's constant enough for other things + (c++/113545). */ + gcc_checking_assert (ctx->quiet); + *non_constant_p = true; + return t; + } + *jump_target = cond; tree body diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-reinterpret3.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-reinterpret3.C new file mode 100644 index 000000000000..adc0b418df91 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-reinterpret3.C @@ -0,0 +1,54 @@ +// PR c++/113545 +// { dg-do run { target c++14 } } + +char foo; + +// This one caught a call to gcc_unreachable in +// cp/constexpr.cc:label_matches, when passed a convert_expr from the +// cast in the call. +constexpr unsigned char swbar(__UINTPTR_TYPE__ baz) +{ + switch (baz) + { + case 13: + return 11; + case 14: + return 78; + case 2048: + return 13; + default: + return 42; + } +} + +// For reference, the equivalent* if-statements. +constexpr unsigned char ifbar(__UINTPTR_TYPE__ baz) +{ + if (baz == 13) + return 11; + else if (baz == 14) + return 78; + else if (baz == 2048) + return 13; + else + return 42; +} + +__attribute__ ((__noipa__)) +void xyzzy(int x) +{ + if (x != 42) + __builtin_abort (); +} + +int main() +{ + unsigned const char c = swbar(reinterpret_cast<__UINTPTR_TYPE__>(&foo)); + xyzzy(c); + unsigned const char d = ifbar(reinterpret_cast<__UINTPTR_TYPE__>(&foo)); + xyzzy(d); + unsigned const char e = swbar((__UINTPTR_TYPE__) &foo); + xyzzy(e); + unsigned const char f = ifbar((__UINTPTR_TYPE__) &foo); + xyzzy(f); +} diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-reinterpret4.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-reinterpret4.C new file mode 100644 index 000000000000..9aaa6e463bc6 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-reinterpret4.C @@ -0,0 +1,54 @@ +// PR c++/113545 +// { dg-do compile { target c++14 } } + +char foo; + +// This one caught a call to gcc_unreachable in +// cp/constexpr.cc:label_matches, when passed a convert_expr from the +// cast in the call. +constexpr unsigned char swbar(__UINTPTR_TYPE__ baz) +{ + switch (baz) + { + case 13: + return 11; + case 14: + return 78; + case 2048: + return 13; + default: + return 42; + } +} + +// For reference, the equivalent* if-statements. +constexpr unsigned char ifbar(__UINTPTR_TYPE__ baz) +{ + if (baz == 13) + return 11; + else if (baz == 14) + return 78; + else if (baz == 2048) + return 13; + else + return 42; +} + +__attribute__ ((__noipa__)) +void xyzzy(int x) +{ + if (x != 42) + __builtin_abort (); +} + +int main() +{ + unsigned constexpr char c = swbar(reinterpret_cast<__UINTPTR_TYPE__>(&foo)); // { dg-error "conversion from pointer type" } + xyzzy(c); + unsigned constexpr char d = ifbar(reinterpret_cast<__UINTPTR_TYPE__>(&foo)); // { dg-error "conversion from pointer type" } + xyzzy(d); + unsigned constexpr char e = swbar((__UINTPTR_TYPE__) &foo); // { dg-error "conversion from pointer type" } + xyzzy(e); + unsigned constexpr char f = ifbar((__UINTPTR_TYPE__) &foo); // { dg-error "conversion from pointer type" } + xyzzy(f); +}
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