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__inline and change of sign warning

Hi all,

I would like to discover why the compiler issues warning #68 (integer conversion resulted in a change of sign) for the code below. It is issued only for -O3, "Optimize for Time" enabled and when the function is inlined (__inline keyword).

I have tried to cast anything which could be implicitly converted to int back to uint, but no chance to get rid of this warning.

armcc.exe V4.0.0.524

static __inline uint8_t IsDecDigit(char c)
{
    return (   (c >= '0')
            && (c <= '9'));
}

...

static void UseIt(void)
{
    char *name;
    ...
    /* Initialize the name to something useful */
    ...
    if (   (IsDecDigit(name[3])) /* <- warning issued for this expression */
        && (IsDecDigit(name[4]))
        && (IsDecDigit(name[5]))
        && (IsDecDigit(name[6]))
    {
        ...
    }
}

Thanks for responses.

Regards Pavel

Parents

0 Pavel Faltynek over 15 years ago in reply to Mike Kleshov

As I see it now, I would rather agree it's just a compiler bug as mentioned somewhere above...
Anyway, there is complete and completely useless example you want ;)
Use the compiler settings mentioned earlier.

#include <stdint.h>
#include <lpc23xx.h>

/*
 * Set to nonzero to remove warnings ;)
 */
#define REMOVE_WARNINGS 0

static char *random_data = (char *)0x40000000;


/*
 * Remove __inline and warnings disappear
 */


static __inline int IsDecDigit(char c)
{
    return (int)((   (c >= (char)'0')
                  && (c <= (char)'9')) ? 1 : 0);
}


static __inline int IsSet(uint32_t flags, uint8_t pos)
{
    return (int)((int)(flags & (1ul << pos)) ? 1 : 0);
}


static DoSomething(uint8_t what)
{
    FIO0CLR = (1ul << what);
}


static DoSomethingElse(uint8_t what)
{
    FIO1SET = (1ul << what);
}


int main(void)
{
    char     *name  = random_data;
    uint32_t  flags = 0;

#if REMOVE_WARNINGS /* Not sure why..., maybe compiler chooses different optimization when there is inline asm? */
    __asm("nop");
#endif

    for (;;)
    {
        if (IsDecDigit(name[0]))
        {
            DoSomething(1);
            flags |= (1ul << 0);
        }

        if (   IsDecDigit(name[1])   /* warning:  #68-D: integer conversion resulted in a change of sign */
            && IsDecDigit(name[2]))
        {
            DoSomething(2);
            flags |= ((1ul << 1) | (1ul << 2));
        }

        if (IsSet(flags, 3))
        {
            DoSomethingElse(3);
        }

        if (   IsSet(flags, 4)       /* warning:  #68-D: integer conversion resulted in a change of sign */
            && IsSet(flags, 5))
        {
            DoSomethingElse(5);
            flags |= 0xf;
        }
    }

/*    return 0;*/
}

Reply

0 Pavel Faltynek over 15 years ago in reply to Mike Kleshov

#include <stdint.h>
#include <lpc23xx.h>

/*
 * Set to nonzero to remove warnings ;)
 */
#define REMOVE_WARNINGS 0

static char *random_data = (char *)0x40000000;


/*
 * Remove __inline and warnings disappear
 */


static __inline int IsDecDigit(char c)
{
    return (int)((   (c >= (char)'0')
                  && (c <= (char)'9')) ? 1 : 0);
}


static __inline int IsSet(uint32_t flags, uint8_t pos)
{
    return (int)((int)(flags & (1ul << pos)) ? 1 : 0);
}


static DoSomething(uint8_t what)
{
    FIO0CLR = (1ul << what);
}


static DoSomethingElse(uint8_t what)
{
    FIO1SET = (1ul << what);
}


int main(void)
{
    char     *name  = random_data;
    uint32_t  flags = 0;

#if REMOVE_WARNINGS /* Not sure why..., maybe compiler chooses different optimization when there is inline asm? */
    __asm("nop");
#endif

    for (;;)
    {
        if (IsDecDigit(name[0]))
        {
            DoSomething(1);
            flags |= (1ul << 0);
        }

        if (   IsDecDigit(name[1])   /* warning:  #68-D: integer conversion resulted in a change of sign */
            && IsDecDigit(name[2]))
        {
            DoSomething(2);
            flags |= ((1ul << 1) | (1ul << 2));
        }

        if (IsSet(flags, 3))
        {
            DoSomethingElse(3);
        }

        if (   IsSet(flags, 4)       /* warning:  #68-D: integer conversion resulted in a change of sign */
            && IsSet(flags, 5))
        {
            DoSomethingElse(5);
            flags |= 0xf;
        }
    }

/*    return 0;*/
}

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