llvm-gcc doesn't support nested functions

[llvmbot]

Bugzilla Link	915
Resolution	FIXED
Resolved on	Feb 22, 2010 12:48
Version	1.8
OS	All
Blocks	llvm/llvm-bugzilla-archive#1166
Reporter	LLVM Bugzilla Contributor
CC	@nlewycky

Extended Description

$ /usr/local/llvm/cfrontend/install/bin/llvm-gcc --emit-llvm -S foo.i -fnested-functions
foo.i: In function ?b?:
foo.i:3: internal compiler error: in lhd_set_decl_assembler_name, at langhooks.c:193
Please submit a full bug report,
with preprocessed source if appropriate.
See URL:http://llvm.org/bugs for instructions.
$ cat foo.i
static void a() {
int foo;
inline void b() {
foo = -1;
}
b();
}

[lattner]

I'm not shocked, we don't support nested functions properly.  I will see if there is something easy we can
do, but we won't supported taking the address of a nested function in the near future.

-Chris

[lattner]

This is dying when trying to codegen the static chain. This would be easy to add support for in llvm-
gcc, but would require intrinsics to represent this and code generator work to implement these. This is
all possible, but not something I have time for. I'll leave this for someone else to pick up.

As a consolation prize, I checked in a patch that causes this to be emitted:

/Users/sabre/asm.c: In function 'b':
/Users/sabre/asm.c:3: sorry, unimplemented: nested functions not supported by LLVM

instead of ICE'ing.

-Chris

[asl]

Testcase from gcc.c-torture

[asl]

Another testcase from gcc.c-torture

[asl]

Another testcase from gcc.c-torture

[asl]

Another testcase from gcc.c-torture

[llvmbot]

Nested subroutines as used in the examples in this PR are now supported.
However there is no support yet for trampolines, i.e. taking the address of a
nested subroutine, nor for non-local gotos. I've opened llvm/llvm-bugzilla-archive#1190 for tracking
progress on trampolines. I didn't bother for non-local gotos because it's
less clear that anyone is interested in that. By the way, the testcase in
attachment 625 still fails to compile, because tree-nested.c goes into an
infinite loop, i.e. this seems to be a gcc bug not an LLVM one.

[llvmbot]

I'm still getting a segfault:
/tmp/delta$ /usr/local/code/llvm/llvm-gcc4/install/bin/gcc --emit-llvm -S foo.i -fnested-functions
gcc: Internal error: Segmentation fault (program cc1)
Please submit a full bug report.
See URL:http://llvm.org/bugs for instructions.
/tmp/delta$ cat foo.i
static void foo(void *a){
inline void foo_bar() {
a += 1;
}
}

[lattner]

Verified, this example doesn't use trampolines, but causes infinite recursion in the FE.

[lattner]

Actually, this looks like an unrelated bug. I've filed it as Bug 1274.

-Chris

[lattner]

Incidentally, many tests from the gcc testsuite fail at -O0, e.g. gcc.c-torture/20010605-1.c

[llvmbot]

Incidentally, many tests from the gcc testsuite fail at -O0, e.g.
gcc.c-torture/20010605-1.c

This fires an assertion I have here locally that checks that
CreateTemporary is not used when the gcc type has variable
size. So at first glance it looks to me like this isn't really
a problem with nested functions as such. Can you please open
a new PR for this.

[lattner]

Done! It is bug 2283