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From: "gabravier at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/107840] New: ICE when compiling cursed setjmp/longjmp that
 uses __builtin_call_with_static_chain
Date: Wed, 23 Nov 2022 16:44:10 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Version: 13.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107840

            Bug ID: 107840
           Summary: ICE when compiling cursed setjmp/longjmp that uses
                    __builtin_call_with_static_chain
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gabravier at gmail dot com
  Target Milestone: ---

typedef __UINT16_TYPE__ uint16_t;
typedef __UINT32_TYPE__ uint32_t;
typedef __INTPTR_TYPE__ intptr_t;
#define unreachable __builtin_unreachable

typedef struct{
        const uint16_t mov1;
        const uint32_t addr;
        const uint16_t mov2;
        const void * const chain;
} __attribute__((packed)) thunk_struct;

#define NESTED_CHAIN(p) ({            \
        thunk_struct *__t =3D (void*)p; \
        __t->chain;                   \
})

#define NESTED_ADDR(p) ({                 \
        auto __p =3D (p);                   \
        thunk_struct *__t =3D (void*)__p;   \
        (typeof(__p))(intptr_t)__t->addr; \
})

#define NESTED_UPGRADE(self, ptr, args) ({                    \
        if(self !=3D ptr)                                       \
                __builtin_call_with_static_chain(             \
                        NESTED_ADDR((typeof(self)*)ptr) args, \
                        NESTED_CHAIN(ptr)                     \
                );                                            \
})

typedef struct{
        // can't apply standard [[noreturn]] to function pointers
        [[gnu::noreturn]] void(*fun)(void*, int);
}xjmp_buf[1];

#define xsetjmp(env) ({                                 \
        __label__ trgt;                                 \
        int __xsetjmp_ret =3D 0;                          \
        [[noreturn]] void __jmp(void *self, int r){     \
                NESTED_UPGRADE(__jmp, self, (self, r)); \
                __xsetjmp_ret =3D r ?: 1;                 \
                goto trgt;                              \
        }                                               \
        env[0].fun =3D __jmp;                             \
        trgt:;                                          \
        int tmp =3D __xsetjmp_ret;                        \
        __xsetjmp_ret =3D 0;                              \
        tmp;                                            \
})

[[noreturn, gnu::always_inline]] inline void xlongjmp(xjmp_buf env, int r){
        ((void(*)(void*, int))NESTED_ADDR(env[0].fun))(env[0].fun, r);
        unreachable();
}

int main(){
        int a =3D 0;
        xjmp_buf test;
        void foo(xjmp_buf ctx){
                if(!xsetjmp(ctx)){
                        (volatile void)0;
                }
        }

        foo(test);
        xlongjmp(test, ++a);
}

Compiling this code with `-std=3Dc2x` results in the following error:

<source>: In function 'foo':
<source>:60:14: error: label '({anonymous})' has incorrect context in bb 4
   60 |         void foo(xjmp_buf ctx){
      |              ^~~
during GIMPLE pass: cfg
dump file: /app/output.c.015t.cfg
<source>:60:14: internal compiler error: verify_flow_info failed
0x2008dee internal_error(char const*, ...)
        ???:0
0xaf90d7 verify_flow_info()
        ???:0
0x10447c7 cleanup_tree_cfg(unsigned int)
        ???:0
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Compiler returned: 1

(PS: I cannot seem to get more of the necessary information from Godbolt,
although the bug seems simple enough to reproduce without it. Still, this l=
ink
to the setup I got the bug in might help: https://godbolt.org/z/cd7f4Mdzd)=