Re: [Tinycc-devel] parsing 0x1e+1 as 0x1e +1

[Vincent Lefevre]

On 2016-04-27 13:06:14 +0300, Sergey Korshunoff wrote:
> > There should be a space between 0x1e and +1 (see for instance, the
> > output of "gcc -E", "clang -E" and "icc -E")
> 
> Space is not required. Check pcc. 0x1e+1 is parsed as 0x1e +1.

So does CompCert 2.4, but IMHO, this is an incorrect interpretation of
the C standard. An error is better than unexpected results due to the
choice done by pcc and CompCert. Here's an example:

#include <stdio.h>

int main(void)
{
  int E = 0;
#define E 1
  printf ("0x%x 0x%x\n", 0x11-E, 0x1e-E);
  return 0;
}

CompCert 2.4 outputs 0x10 0x1e (following its interpretation of 6.4.8)
though if the user expects a subtraction in both cases, he probably
expects that E yields the same value in both cases. But this is not
what one gets (E yields 1 in 0x11-E, but 0 in 0x1e-E).

> If icc/gcc/clang. complain, then this is theire problem. eE is valid
> exp char only for decimal notation. And for hexadeciamal notation it
> is an ordinal digit char.

No, this is not what the C standard says. Transformations are described
in terms of tokentization.

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Vincent Lefèvre <address@hidden> - Web: <https://www.vinc17.net/>
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