Re: [Tinycc-devel] tcc segfaults with complex struct initialization

[Michael Matz]

Hi,

On Wed, 16 Mar 2016, Assaf Gordon wrote:

>     $ git clone git://git.sv.gnu.org/coreutils.git && cd coreutils
>     $ ./bootstrap
>     $ ./configure --without-selinux CC=tcc
>     $ make V=1

Thanks for the report.

> The offending code is a complex struct initialization, perhaps related to
> recent discussion:
>   http://lists.nongnu.org/archive/html/tinycc-devel/2016-03/msg00042.html

Not directly, it's more an extension in that our initializer parsing is 
heavily confused when some initializers are structs themself.  I.e. the 
particular situation TCC stumbles upon is:

struct S { long j;};
struct T { struct S t;};
struct S ts = {0};
void foo (void)
{
  struct T its = { ts };
}

So, the struct field its.t (of type struct S) is supposed to be 
initialized by the variable ts (also of type struct S).  But our struct 
initializer parsing is confused, recursing eagerly into the LHS its.struct 
S, seeing member its.S.j of type long and then is surprised that the 
initializer for this long is of type 'struct S' (namely still the ts 
variable).

I.e. either there's lock-step recursion missing (i.e. when going into 
its.S.j it should also go into ts.j), or detection of the situation that a 
struct initializer can also be a full struct itself.  The latter seems 
more correct and easier, but the routines are a slight mess, so I'd need 
to think a bit about this (or wait for somebody else :) ).

(I do think we had some other reports about this or similar situations as 
well).


Ciao,
Michael.