Bug 22884 – ImportC: function does not decay to pointer when being cast

The following C code fails to compile. This kind of pointer cast can be seen in sqlite and also in some C library APIs like python. int printf(const char*, ...); typedef void (*funcptr)(void); funcptr a = printf; // ok funcptr b = (funcptr)printf; // Error: non-constant expression `printf` funcptr foo(void){ funcptr f = (funcptr)printf; // ok return f; }

(In reply to dave287091 from comment #0) > The following C code fails to compile. This kind of pointer cast can be seen > [...] I have discovered that changing funcptr b = (funcptr)printf; to funcptr b = (funcptr)&printf; will compile. So it might be that the function expression is not decaying to a function pointer before the cast.

(In reply to dave287091 from comment #1) > (In reply to dave287091 from comment #0) > > The following C code fails to compile. This kind of pointer cast can be seen > > [...] Also, it looks like this function does error, compilation was just not reaching that point due to the previous error. typedef void (*funcptr)(void); funcptr foo(void){ funcptr f = (funcptr)printf; // Error: e2ir: cannot cast `printf` of type `extern (C) int(const(char)*, ...)` to type `extern (C) void function() return f; } Probably same problem, it’s not decaying to a function pointer when it should.

@WalterBright created dlang/dmd pull request #13842 "fix Issue 22884 - ImportC: function does not decay to pointer when be…" fixing this issue: - fix Issue 22884 - ImportC: function does not decay to pointer when being cast https://github.com/dlang/dmd/pull/13842

*** Issue 22893 has been marked as a duplicate of this issue. ***

dlang/dmd pull request #13842 "fix Issue 22884 - ImportC: function does not decay to pointer when be…" was merged into master: - 383d9c376918fc0e0fc216e27946a58156c3eaa5 by Walter Bright: fix Issue 22884 - ImportC: function does not decay to pointer when being cast https://github.com/dlang/dmd/pull/13842