[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551 Nathan Sidwell changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution|--- |FIXED --- Comment #15 from Nathan Sidwell --- Fixed on 5, 6 & HEAD
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551 --- Comment #14 from Nathan Sidwell --- Author: nathan Date: Thu Dec 8 19:27:32 2016 New Revision: 243457 URL: https://gcc.gnu.org/viewcvs?rev=243457&root=gcc&view=rev Log: PR c++/78551 * constexpr.c (extract_string_elt): New. Broken out of ... (cxx_eval_array_reference): ... here. Call it. (cxx_eval_store_expression): Convert init by STRING_CST into CONSTRUCTOR, if needed. PR c++/78551 * g++.dg/cpp1y/pr78551.C: New. Added: branches/gcc-5-branch/gcc/testsuite/g++.dg/cpp1y/pr78551.C Modified: branches/gcc-5-branch/gcc/cp/ChangeLog branches/gcc-5-branch/gcc/cp/constexpr.c branches/gcc-5-branch/gcc/testsuite/ChangeLog
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551 --- Comment #13 from Nathan Sidwell --- Author: nathan Date: Thu Dec 8 18:37:03 2016 New Revision: 243451 URL: https://gcc.gnu.org/viewcvs?rev=243451&root=gcc&view=rev Log: PR c++/78551 * constexpr.c (extract_string_elt): New. Broken out of ... (cxx_eval_array_reference): ... here. Call it. (cxx_eval_store_expression): Convert init by STRING_CST into CONSTRUCTOR, if needed. PR c++/78551 * g++.dg/cpp1y/pr78551.C: New. Added: branches/gcc-6-branch/gcc/testsuite/g++.dg/cpp1y/pr78551.C Modified: branches/gcc-6-branch/gcc/cp/ChangeLog branches/gcc-6-branch/gcc/cp/constexpr.c branches/gcc-6-branch/gcc/testsuite/ChangeLog
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551 --- Comment #12 from Nathan Sidwell --- Author: nathan Date: Thu Dec 8 18:34:04 2016 New Revision: 243448 URL: https://gcc.gnu.org/viewcvs?rev=243448&root=gcc&view=rev Log: PR c++/78551 * constexpr.c (extract_string_elt): New. Broken out of ... (cxx_eval_array_reference): ... here. Call it. (cxx_eval_store_expression): Convert init by STRING_CST into CONSTRUCTOR, if needed. PR c++/78551 * g++.dg/cpp1y/pr78551.C: New. Added: trunk/gcc/testsuite/g++.dg/cpp1y/pr78551.C Modified: trunk/gcc/cp/ChangeLog trunk/gcc/cp/constexpr.c trunk/gcc/testsuite/ChangeLog
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551 Nathan Sidwell changed: What|Removed |Added Status|NEW |ASSIGNED
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551 --- Comment #11 from Nathan Sidwell --- Created attachment 40276 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40276&action=edit non-union crash Union is not necessary to trigger the ICE. All we need is to initialize a char array with a string constant, and then try and write an element of the array.
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551 --- Comment #10 from Vlad Petric --- Could someone boost its priority? Given that gcc segfaults with valid code (see newest example/attachment), I believe it's worth a P1.
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551 --- Comment #9 from Vlad Petric --- Created attachment 40235 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40235&action=edit Compliant code that segfaults the compiler
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551
--- Comment #8 from Vlad Petric ---
(In reply to Vlad Petric from comment #7)
> Ok, so the example that I started this bug with is not standard compliant
> because it initialized different elements in a union with the constexpr
> constructor.
>
> The following does just one. I believe that the following is
> standard-compliant code (though obviously I could be wrong)
>
> And it generates a segfault.
>
> struct A {
> union {
> long s;
> char d[4];
> };
> constexpr A (char x) : d("") { d[0] = x; }
> };
>
> A a{'a'};
clang 3.8/4.0 have no problem with the above code.
Personally I think that we should change the main attachment and the tag - to
segfault on valid code (worse than ICE ...).
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551
--- Comment #7 from Vlad Petric ---
Ok, so the example that I started this bug with is not standard compliant
because it initialized different elements in a union with the constexpr
constructor.
The following does just one. I believe that the following is standard-compliant
code (though obviously I could be wrong)
And it generates a segfault.
struct A {
union {
long s;
char d[4];
};
constexpr A (char x) : d("") { d[0] = x; }
};
A a{'a'};
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551 Richard Biener changed: What|Removed |Added Priority|P3 |P2
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551
Jakub Jelinek changed:
What|Removed |Added
CC||jason at gcc dot gnu.org
--- Comment #6 from Jakub Jelinek ---
Actually, no array is needed,
struct A { union { short s; char d[2]; }; constexpr A (char x) : s(0x2020) {
d[0] = x; } };
A c { 'a' };
ICEs as well. The C++ FE creates a CONSTRUCTOR that contains both initializer
for s as well for d[0], that obviously can't be emitted properly.
Before Nathan's fix, GCC just emitted garbage:
.type c, @object
.size c, 2
c:
.value 8224
.byte 97
.zero 1
i.e. c actually didn't have size 2, but 4.
struct A { union { short s; char d[2]; }; constexpr A (const char x) :
s(0x2020) { d[0] = x; } };
constexpr A c { 'a' };
const A *p = &c;
is rejected by clang++, because of:
assignment to member 'd' of union with active member 's' is not allowed in a
constant expression
g++ still ICEs.
Finally:
struct A { union { short s; char d[2]; }; constexpr A (const char x) : d{0,0} {
d[0] = x; d[1] = x; } };
constexpr A c { 'a' };
const A *p = &c;
is accepted by both compilers and looks good.
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551
Jakub Jelinek changed:
What|Removed |Added
CC||jakub at gcc dot gnu.org
--- Comment #5 from Jakub Jelinek ---
Reduced testcase:
struct A { union { long s; char d[1]; }; constexpr A (char x) : s(0) { d[0] =
x; } };
struct B { A b[2]; };
B c { 'a', 'b' };
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551 Martin Liška changed: What|Removed |Added Status|UNCONFIRMED |NEW Last reconfirmed||2016-11-28 CC||marxin at gcc dot gnu.org, ||nathan at gcc dot gnu.org Known to work||5.3.0 Ever confirmed|0 |1 --- Comment #4 from Martin Liška --- Confirmed, started on trunk with r234636. It was also backported to GCC 5.4.0.
[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551
Richard Biener changed:
What|Removed |Added
Keywords||ice-on-invalid-code
Known to work||4.9.4
Target Milestone|--- |5.5
Summary|Internal compiler error |[5/6/7 Regression] Internal
|with constexpr |compiler error with
|initialization of union |constexpr initialization of
||union
Known to fail||5.4.0, 6.2.0, 7.0
--- Comment #3 from Richard Biener ---
ICEs in
t.C:20:53: internal compiler error: in output_constructor_regular_field, at
varasm.c:4968
constexpr std::array array({"long", "longer"});
^
GCC 4.9 rejects it, so does clang++:
> clang++ t.C -S -std=gnu++14
t.C:20:28: error: constexpr variable 'array' must be initialized by a constant
expression
constexpr std::array array({"long", "longer"});
^
t.C:14:22: note: assignment to member 'buff' of union with active member 's' is
not allowed in a constant expression
buff[i] = str[i];
^
t.C:20:35: note: in call to 'A(&"long"[0])'
constexpr std::array array({"long", "longer"});
^
1 error generated.
Backtrace from GCC 6 branch head:
> /space/rguenther/install/gcc-6.2/bin/g++ t.ii -B /abuild/rguenther/gcc6-g/gcc
t.C:20:53: internal compiler error: in output_constructor_regular_field, at
varasm.c:4968
constexpr std::array array({"long", "longer"});
^
0x14386b5 output_constructor_regular_field
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:4968
0x14394c1 output_constructor
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:5276
0x1437f16 output_constant
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:4803
0x143897b output_constructor_regular_field
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:5006
0x14394c1 output_constructor
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:5276
0x1437f16 output_constant
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:4803
0x143897b output_constructor_regular_field
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:5006
0x14394c1 output_constructor
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:5276
0x1437bd8 output_constant
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:4773
0x143897b output_constructor_regular_field
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:5006
0x14394c1 output_constructor
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:5276
0x1437f16 output_constant
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:4803
0x142f4d9 assemble_variable_contents
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:2062
0x142fe82 assemble_variable(tree_node*, int, int, int)
/space/rguenther/src/svn/gcc-6-branch/gcc/varasm.c:2238
0x1447096 varpool_node::assemble_decl()
/space/rguenther/src/svn/gcc-6-branch/gcc/varpool.c:582
0xbb40d9 output_in_order
/space/rguenther/src/svn/gcc-6-branch/gcc/cgraphunit.c:2231
0xbb4784 symbol_table::compile()
/space/rguenther/src/svn/gcc-6-branch/gcc/cgraphunit.c:2468
0xbb49c3 symbol_table::finalize_compilation_unit()
/space/rguenther/src/svn/gcc-6-branch/gcc/cgraphunit.c:2564
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