[9fans] 8c (pcc) bug??

[9fans] 8c (pcc) bug??

[tapique]

seems like 8c compiler doesn't like apostrophes in // comments:

// we don't have the value yet
       doesn't work, while
// we dont have the value yet
       works.
Tried with pcc, not directly 8c. Should not matter, however.

++pac


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Re: [9fans] 8c (pcc) bug??

[boyd, rounin]

this is one nasty bug.

the problem is the // and /* comments are parsed twice:

    1) in a #define
    2) in an ordinary code block

the assumption that /sys/src/cmd/cc/macbody makes [case #1] is that
a #define consists of a:

    - name
    - optional list of args
    - list of names (possibly arguments)
    - line continuations
    - comments
    - characters

should you have the misfortune to:

    #define S "//...

or

    #define  S "/*...

you get:

    #define S "

and you are in a "world of pain".

to my mind it should be taught about strings, but this is somewhat non-trivial.

well, maybe not.  it needs to know about comments to skip arguments that
maybe are hidden away in comment.  ahh, this give me an idea.

/sys/src/cmd/cc/lex.c [case 2] goes to some effort to lex up strings and pass
them up to yacc.  it uses esschar() which decodes chars & Runes in char and
string constants, Rune by Rune.

i'm not a language lawyer, nor do i have copies of the numerous standards,
but do i do believe that:

    #define S "//foo"

should give me:

    "//foo"

hmm, yeah, i think i have a fix.
--
MGRS 31U DQ 52572 12604

Re: [9fans] 8c (pcc) bug??

[boyd, rounin]

i think if the following diff if applied to /sys/src/cmd/cc/macbody
it should fix this nasty bug.  it's not amazingly well tested, but if
you're in a position to or are feeling brave, please do so


236a237,264
>   if (c == '\'' || c == '"') {
>    int e;
>
>    base = allocn(base, len, 1);
>    base[len++] = c;
>    e = c;
>
>    for (;;) {
>     int p;
>
>     p = c;
>     if ((c = getc()) == '\n')
>      break;
>
>     base = allocn(base, len, 1);
>     base[len++] = c;
>
>     if (p == '\\' && c == e)
>      continue;
>
>     if (c == e) {
>      c = getc();
>      break;
>     }
>    }
>
>    continue;
>   }
--
MGRS 31U DQ 52572 12604

Re: [9fans] 8c (pcc) bug??

[C H Forsyth]

the reason i mentioned that i `thought' i had a fix
was that i wanted to think whether there was any
code that relied on a property of the existing implementation,
which i kept, somewhat messily, but boyd's tidier change doesn't.

the answer is ... /sys/include/libc.h:/^#define.*assert

Re: [9fans] 8c (pcc) bug??

[boyd, rounin]

russ has pointed out that my fix has bugs, so don't apply it.

i'm gonna have another look "i'm sure it's down here somewhere".
--
MGRS 31U DQ 52572 12604

Re: [9fans] 8c (pcc) bug??

[Charles Forsyth]

>>Tried with pcc, not directly 8c. Should not matter, however.

you need to give -+ to pcc to have it (or rather underlying cpp) support c++ comments.

8c alone is fine