Re: [Tinycc-devel] [BUG] [PATCH] tcc and INT64: wrong result of comparison (a test included)

[Sergey Korshunoff]

tccpp(parse_number): changes to detect a constat type correctly.
This patch is tested with a nimrod compiler build process. All works.

2015-01-05 2:03 GMT+03:00, Sergey Korshunoff <address@hidden>:
> There is another approach: assume the constant is negative by default.
> This is the method used in nimrod to scan a constants:
> lib/pure/parseutils.nim(rawparse)
>
> proc rawParseInt(s: string, b: var BiggestInt, start: int = 0): int =
> var
>     sign: BiggestInt = -1                 # minus by defaul
>     i = start
>   if s[i] == '+': inc(i)
>   elif s[i] == '-':
>     inc(i)
>     sign = 1
>   if s[i] in {'0'..'9'}:
>     b = 0
>     while s[i] in {'0'..'9'}:
>       b = b * 10 - (ord(s[i]) - ord('0')) #!  the point
>       inc(i)
>       while s[i] == '_': inc(i) # underscores are allowed and ignored
>     b = b * sign
>     result = i - start
>
>
> Sun, 04 Jan 2015 16:51 +0000, Thomas Preud'homme <address@hidden>:
>> Le dimanche 4 janvier 2015, 19:18:34 Sergey Korshunoff a écrit :
>>> By replacing a -2147483648 with a -2147483647 I can succesfully build
>>> a working nim compiler. But this is not so good...
>>
>> The bug is in tccpp.c parse_number. The function tries to guess what
>> should
>> be
>> the size and sign of the litteral before parsing the suffix (which might
>> not
>>
>> exist).
>>
>>         /* XXX: not exactly ANSI compliant */
>>         if ((n & 0xffffffff00000000LL) != 0) {
>>             if ((n >> 63) != 0)
>>                 tok = TOK_CULLONG;
>>             else
>>                 tok = TOK_CLLONG;
>>         } else if (n > 0x7fffffff) {
>>             tok = TOK_CUINT;
>>         } else {
>>             tok = TOK_CINT;
>>         }
>>
>> In your case it will pass in the first else if and set tok to TOK_CUINT.
>> So
>> far
>> so good.
>>
>> Then it will parse the suffix and when it sees the second L it does this:
>>
>>                     if (tok == TOK_CINT)
>>                         tok = TOK_CLLONG;
>>                     else if (tok == TOK_CUINT)
>>                         tok = TOK_CULLONG;
>>
>> So here it will set the value to TOK_CULLONG while it should set it to
>> TOK_CLLONG and warn if the value is too big.
>>
>> My feeling is that the automatic guess for the size and sign should be
>> done
>>
>> after trying to look for a suffix.
>>
>> The algorithm would be something like:
>>
>> 1) Set tok to TOK_CINT and suffix_found to false.
>> 2) Then look for a L or U suffix with unchanged code except for setting a
>> suffix_found variable if any such suffix is found.
>> 3) Then if suffix_found is false try automatic detection, otherwise warn
>> of
>>
>> overflow and possibly process the overflow (what does GCC does in this
>> case?) Be
>> careful about the sign when checking for overflow.
>>
>> Do you want to take a stab at it?
>>
>> Best regards,
>>
>> Thomas
>>
>

2015-01-05-3-tccpp-parse-number.patch
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