https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71564
Bug ID: 71564
Summary: label inside a lambda conflicts (?) with another one
outside it
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: lh_mouse at 126 dot com
Target Milestone: ---
This code fails to compile with any current version of g++ from 4.7 to 7.0:
```
int main(){
_infinite_retry:
[=]{
_infinite_retry:
goto _infinite_retry; // go to the second _infinite_retry.
}();
goto _infinite_retry; // go to the first _infinite_retry.
}
```
D:\Desktop>g++ test.cpp -Wall
test.cpp: In function 'int main()':
test.cpp:2:2: warning: label '_infinite_retry' defined but not used
[-Wunused-label]
_infinite_retry:
^~~~~~~~~~~~~~~
test.cpp:7:8: error: label '_infinite_retry' used but not defined
goto _infinite_retry; // go to the outer _infinite_retry.
^~~~~~~~~~~~~~~
Quoting from the standard:
```
ISO/IEC WG21 N4582
5.1.2 Lambda expressions [expr.prim.lambda]
8 The lambda-expression’s compound-statement yields the function-body (8.4) of
the function call operator, ...
3.3.5 Function scope [basic.funscope]
1 Labels (6.1) have function scope and may be used anywhere in the function in
which they are declared. Only
labels have function scope.
```
The compound statement of a lambda expression is a function body thus it
creates a function scope. The second label should reside in that scope but
somehow nullifies the first one, causing the second goto statement to fail to
find the first label.
