https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86243
Bug ID: 86243
Summary: unknown attributes causing hard error
Product: gcc
Version: 7.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: h2+bugs at fsfe dot org
Target Milestone: ---
The following code (based on
http://open-std.org/JTC1/SC22/WG21/docs/papers/2017/p0479r1.html)
int main()
{
if (1 == 2) [[unlikely]]
throw int{};
return 2;
}
produces an error:
% g++7 -std=c++17 test.cpp
test.cpp: In function 'int main()':
test.cpp:3:18: error: expected identifier before '[' token
if (1 == 2) [[unlikely]]
^
test.cpp: In lambda function:
test.cpp:4:9: error: expected '{' before 'throw'
throw int{};
^~~~~
test.cpp: In function 'int main()':
test.cpp:4:9: error: expected ';' before 'throw'
This strongly looks like a bug. If one encloses the if-block in braces, I
instead get a warning:
int main()
{
if (1 == 2) [[unlikely]]
{
throw int{};
}
return 2;
}
results in:
% g++7 -std=c++17 test.cpp
test.cpp: In function 'int main()':
test.cpp:3:17: warning: attributes at the beginning of statement are ignored
[-Wattributes]
if (1 == 2) [[unlikely]]
^
Note that I am not even setting -Wall or -Wextra. Even then I would think that
unknown attributes should just be silently ignored as suggested by the
standard, or not?
Thanks for your help!
Tested versions:
g++7 (FreeBSD Ports Collection) 7.3.1 20180531
g++8 (FreeBSD Ports Collection) 8.1.1 20180608
g++9 (FreeBSD Ports Collection) 9.0.0 20180603 (experimental)
