[Bug c++/79184] New: -Wint-in-bool-context triggered erroneously in template parameter

[jagerman at jagerman dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79184

Bug ID: 79184
   Summary: -Wint-in-bool-context triggered erroneously in
template parameter
   Product: gcc
   Version: 7.0
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: jagerman at jagerman dot com
  Target Milestone: ---

When compiling the following with -Wint-in-bool-context under a recent snapshot
of g++-7:



template  void f(int) {}
template  void f() {}

int main() {
f<1*1>();
}


`g++ -Wint-in-bool-context t.cpp' produces the warning:

t.cpp: In function 'int main()':
t.cpp:5:8: warning: '*' in boolean context, suggest '&&' instead
[-Wint-in-bool-context]
 f<1*1>();
   ~^~

But this is wrong: the template parameter here is int, not a bool, and is not
in bool context.  The existence of the templated overload, despite not being
called in this context, appears to be falsely triggering the warning.

[Bug c++/80334] New: Segfault when taking address of copy of unaligned struct

[jagerman at jagerman dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80334

Bug ID: 80334
   Summary: Segfault when taking address of copy of unaligned
struct
   Product: gcc
   Version: 7.0
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: jagerman at jagerman dot com
  Target Milestone: ---

I am getting a segfault with g++ 7 when trying to copy an unaligned struct into
an aligned variable when the struct contains a member with alignment greater
than 8 (on my amd64 architecture).

I boiled my code down into the following simplified program which exhibits the
segfault under a recent g++ 7 snapshot (requires compiling with -O2 or above to
trigger):

test.cpp
=
#include 

struct A { alignas(16) char c; };
struct B { A unpacked; char d; } __attribute__((packed));

int main() {
std::cout << "sizeof(A) = " << sizeof(A) << ", sizeof(B) = " << sizeof(B)
<< "\n";
alignas(16) B b[3];

for (int i = 0; i < 3; i++) b[i].unpacked.c = 'a' + i;

for (int i = 0; i < 3; i++) {
std::cout << "i=" << i << "; copying..." << std::endl;
auto a = new A(b[i].unpacked);
std::cout << "copied value = " << a->c << std::endl;
}
}
=



If I change the `alignas(16)` on the member in `struct A` to `alignas(8)` or
`alignas(4)` there is no segfault; there also is no segfault under -O0 or -O1,
or under g++ 6.

(The `alignas(16) char` was a `long double` in the original code, which has
alignof == 16).

The alignas(16) on the array in main is just there to force alignment on the
first element of `b`: with that alignment, the *first* copy succeeds because
the `unpacked` member happens to be correctly aligned; the call in the second
iteration of the loop (when the member isn't aligned) triggers the segfault.

[Bug tree-optimization/80334] [5/6 Regression] Segfault when taking address of copy of unaligned struct

[jagerman at jagerman dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80334

--- Comment #6 from Jason Rhinelander  ---
Confirming that this solves the original (unsimplified) issue for me with
current trunk.