[Bug c++/63732] New: constexpr is not constant expression, when cast member data pointer to data parent type

[Bug c++/63732] New: constexpr is not constant expression, when cast member data pointer to data parent type

[pavel.kral at omsquare dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63732

            Bug ID: 63732
           Summary: constexpr is not constant expression, when cast member
                    data pointer to data parent type
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pavel.kral at omsquare dot com

The code bellow returns error on 4.9.2 (and cause ICE on 4.8.x) tested on
Linux, MinGW and arm-none-eabi. While 'xxx' compiles just fine, 'yyy' which is
casted to parent type doesn't. Just for clarification static const array
'm_members' compiles fine and generate values at compile time in .rodata
section as expected (arm-none-eabi).

class PropertyBase {};
class Number : PropertyBase {};

class ComplexProperty : PropertyBase {
public:
    Number m_firstNumber;
    static PropertyBase ComplexProperty::* const m_members[];

    // compiles fine
    static constexpr auto xxx = (Number
ComplexProperty::*)&ComplexProperty::m_firstNumber;

    //  error: '(PropertyBase
ComplexProperty::*)&ComplexProperty::m_firstNumber' is not a constant
expression
    static constexpr auto yyy = (PropertyBase
ComplexProperty::*)&ComplexProperty::m_firstNumber;
};

// compiles fine
PropertyBase ComplexProperty::* const ComplexProperty::m_members[] = {
        (PropertyBase ComplexProperty::*) &ComplexProperty::m_firstNumber
};

static ComplexProperty person;

int main() {

}

[Bug c++/63732] constexpr is not constant expression, when cast member data pointer to data parent type

[daniel.kruegler at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63732

Daniel Krügler <daniel.kruegler at googlemail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |daniel.kruegler@googlemail.
                   |                            |com

--- Comment #1 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
I disagree with your interpretation. Note that in your code example for yyy
there is an effective C-cast or reinterpret_cast. This is so, because your are
attempting to convert an address to a pointer of member of type

Number ComplexProperty::*

to

PropertyBase ComplexProperty::*

Irrespective of the private base classes, this kind of pointer conversion is
not allowed without a reinterpret_cast, but reinterpret_casts are not valid in
constants expressions.

The conversion to xxx is valid, because there is no type change involved
(Number ComplexProperty::* is converted to Number ComplexProperty::*) and for
the out-of-class member ComplexProperty::m_members definition the code is
well-formed, because you do have an effective reinterpret_cast but not in a
place where a constant expression would be required.
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ida887

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Indeed.

[Bug c++/63732] constexpr is not constant expression, when cast member data pointer to data parent type

[pavel.kral at omsquare dot com]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="UTF-8", Size: 4509 bytes --]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63732

Pavel Král <pavel.kral at omsquare dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #2 from Pavel Král <pavel.kral at omsquare dot com> ---
Hi Daniel,

your are right about effective reintepret_cast<>, thanks for clarification.

Best Regards,
Pavel
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From: "joel at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug debug/63741] New: lm32 ICE in dwarf2out_frame_debug_expr, at dwarf2cfi.c:1677
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idc741

            Bug ID: 63741
           Summary: lm32 ICE in dwarf2out_frame_debug_expr, at
                    dwarf2cfi.c:1677
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: joel at gcc dot gnu.org

Created attachment 33886
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id3886&actioníit
Preprocessed RTEMS fastlz.c which produces the error.

The attached preprocessed code gives an ICE at -O0, -O1, -O2, and -0s. Dropping
the -g gets by the ICE so this seems like  a debug info issue.

lm32-rtems4.11-gcc -O0 -g  -c fastlz.c


lm32-rtems4.11-gcc --pipe -DHAVE_CONFIG_H   -I..
-I../../cpukit/../../../milkymist/lib/include -DRTEMS_RTL_RAP_LOADER=1
-DRTEMS_RTL_ELF_LOADER=1   -mbarrel-shift-enabled -mmultiply-enabled
-mdivide-enabled -msign-extend-enabled -O2 -g -Wall -Wmissing-prototypes
-Wimplicit-function-declaration -Wstrict-prototypes -Wnested-externs -MT
libdl_a-fastlz.o -MD -MP -MF .deps/libdl_a-fastlz.Tpo -c -o libdl_a-fastlz.o
`test -f 'fastlz.c' || echo
'../../../../../../rtems/c/src/../../cpukit/libdl/'`fastlz.c
In file included from
../../../../../../rtems/c/src/../../cpukit/libdl/fastlz.c:113:0:
../../../../../../rtems/c/src/../../cpukit/libdl/fastlz.c: In function
'fastlz1_compress':
../../../../../../rtems/c/src/../../cpukit/libdl/fastlz.c:418:1: internal
compiler error: in dwarf2out_frame_debug_expr, at dwarf2cfi.c:1677
 }
 ^
0x52e8b6 dwarf2out_frame_debug_expr
    ../../gcc-4.9.1/gcc/dwarf2cfi.c:1675
0x52ef6c dwarf2out_frame_debug
    ../../gcc-4.9.1/gcc/dwarf2cfi.c:2043
0x52ef6c scan_insn_after
    ../../gcc-4.9.1/gcc/dwarf2cfi.c:2369
0x5307d2 scan_trace
    ../../gcc-4.9.1/gcc/dwarf2cfi.c:2526
0x5311d5 create_cfi_notes
    ../../gcc-4.9.1/gcc/dwarf2cfi.c:2565
0x5311d5 execute_dwarf2_frame
    ../../gcc-4.9.1/gcc/dwarf2cfi.c:2925
0x5311d5 execute
    ../../gcc-4.9.1/gcc/dwarf2cfi.c:3421
Please submit a full bug report,
with preprocessed source if appropriate.