[Bug c/22346] New: Miscompilation (infinite loop & longjmp?)

["sxanth at ceid dot upatras dot gr" <gcc-bugzilla at gcc dot gnu dot org>]

I really hope this is a bug in my code and not a gcc bug otherwise it looks
serious. The problem basically is that we have an infinite for(;;) loop which
calls a function and adds its return value to a local variable 'sum'.
The loop is terminated with a longjmp.

If the program is compiled at -O0 everything is ok and 'sum' has the sum.
If compiled with >-O1 the sum is always zero.
If we enable a printf printing the value of sum in each iteration, the
result is correct.

The reduced testcase is this:

/////////////////////////////////////////////////////////////////////////////////
/* lightweight c++ 1.4 */

/************** system headers **************/

#include <stdio.h>

#include <setjmp.h>

/************** global scope **************/
struct A;

/************** Structures **************/
struct A_ViRtUaLTaBlE_StRuCt {
    int (*next_APSA1_virtual) (struct A * const this);
};
struct A {
    int c;
    struct A_ViRtUaLTaBlE_StRuCt *const _v_p_t_r_;
};
struct AuToDt_t {
    const struct AuToDt_t *X;
    void *x;
    void *(*y) (void *);
};
struct longjmp_StaCk {
    jmp_buf *x;
    struct longjmp_StaCk *y;
    void *X;
    const struct AuToDt_t *i;
};

/************** Virtua Table declarations **************/
static struct A_ViRtUaLTaBlE_StRuCt A_A_ViRtUaLTaBlE;

/************* Function Prototypes  ************/
static inline void A_ctor_(struct A *const this);
static inline int A_next_(struct A *const this);
void *malloc(unsigned int);
void free();

/************* Global variables **************/
struct longjmp_StaCk longjmp_iNiTObjFaKe, *__restrict longjmp_StaCkTop =
    &longjmp_iNiTObjFaKe;
void __lwc_unwind(void *) __attribute__ ((noreturn));
void __lwc_unwind(void *X)
{
    longjmp_StaCkTop->X = X;
    while (longjmp_StaCkTop->i) {
	longjmp_StaCkTop->i->y(longjmp_StaCkTop->i->x);
	longjmp_StaCkTop->i = longjmp_StaCkTop->i->X;
    }
    longjmp(*longjmp_StaCkTop->x, 1);
}
static inline void *__lwcbuiltin_get_estack()
{
    return longjmp_StaCkTop;
}
static inline void __lwcbuiltin_set_estack(void *v)
{
    longjmp_StaCkTop = v;
}


/************ Internal Functions  *************/
static inline void A___ICoNsTRuCTion(struct A *x, const int y)
{
    int i;
    for (i = 0; i < y; i++) {
	struct A *X = &x[i];
	*(struct A_ViRtUaLTaBlE_StRuCt * *) &X->_v_p_t_r_ = &A_A_ViRtUaLTaBlE;
    }
}
static inline int next_APSA1_virtual(struct A *const this)
{
    return this->_v_p_t_r_->next_APSA1_virtual(this);
}


/********* Program function definitions *********/
static inline void A_ctor_(struct A *const this)
{
    this->c = 0;
}
static inline int A_next_(struct A *const this)
{
    if (this->c > 10)
	__lwc_unwind(0);
    return this->c++;
}

int main()
{
    struct A *a = ({
		   struct A * lwcUniQUe = (struct A *)malloc(sizeof(struct A));
		   A___ICoNsTRuCTion(lwcUniQUe, 1); A_ctor_(lwcUniQUe); lwcUniQUe;}
    );
    int sum = 0;
    {
	struct longjmp_StaCk longjmp_CoNtExT;
	jmp_buf lwcUniQUe2;
	longjmp_CoNtExT.x = &lwcUniQUe2;
	longjmp_CoNtExT.y = longjmp_StaCkTop;
	longjmp_StaCkTop = &longjmp_CoNtExT;
	longjmp_CoNtExT.X = 0;
	longjmp_CoNtExT.i = 0;
	if (!(setjmp(lwcUniQUe2))) {
	    {
		for (;;) {
		    sum += next_APSA1_virtual(a);
//		    printf("sum=%i\n", sum);
		}
	    }
	    longjmp_StaCkTop = longjmp_CoNtExT.y;
	} else {
	    longjmp_StaCkTop = longjmp_CoNtExT.y;
	}
    }
    printf("%i\n", sum);
    return 0;
}

/**************** Virtual tables ****************/
static struct A_ViRtUaLTaBlE_StRuCt A_A_ViRtUaLTaBlE = { .next_APSA1_virtual =
A_next_,} ;
///////////////////////////////////////////////////////////////////////////

-- 
           Summary: Miscompilation (infinite loop & longjmp?)
           Product: gcc
           Version: 3.4.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: sxanth at ceid dot upatras dot gr
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22346