templated lambda with {} cause GC

[rikki cattermole]

On 10/08/2018 9:57 PM, learnfirst1 wrote:
> 
> import core.stdc.stdio;
> 
> struct Test {
>      string name ;
> }
> 
> void T(alias pred, A...)(){
>      __gshared t = Test(A) ;
>       pred(t);
> }
> 
> extern(C) void main(){
>      T!(t => printf("test 1 name = %s\n".ptr, t.name.ptr), "test") ; // 
> build OK
>      T!(t => {
>          printf("test 2 name = %s\n".ptr, t.name.ptr);
>      }, "test") ; // build error
> }
> 
> --------------
> 
> build this with betterC
> 
> Undefined symbols for architecture x86_64:
>    "__d_allocmemory", referenced from:
>        __D4test4mainUZ__T9__lambda2TSQBb4TestZQvFNaNbNfQtZDFNbNiZv in 
> test.o
> ld: symbol(s) not found for architecture x86_64
> clang: error: linker command failed with exit code 1 (use -v to see 
> invocation)
> Error: linker exited with status 1
> 
> 
> to use without {}, it work as expect.
> 
> Is there a way to avoid this GC with {}, because we need multi line here.

Without the brackets it is inferring to not have state and hence is a 
function. But with the brackets it is assuming there is state required 
and hence has to allocate. Without manually allocating said state (not 
what you want), you cannot do this.