344135 - jsgc.c line 323 won't compile in DEBUG

Status: RESOLVED WONTFIX

(Core :: JavaScript Engine, defect)

Description

[Mike Moening]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.8.0.4) Gecko/20060508 Firefox/1.5.0.4
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.8.0.4) Gecko/20060508 Firefox/1.5.0.4

jsgc.c line 323 is broke and won't compile in DEBUG.

Here's the offending line of code:

--------------------------------------------------
JS_STATIC_ASSERT(2 <= sizeof table->array[0]);
--------------------------------------------------

Here's the compiler errors:
------------------------------------------
syntax error : missing ')' before '+'
syntax error : missing ';' before '+'
syntax error : ')'
subscript requires array or pointer type
------------------------------------------

Compiled using VC++ 6.0 with the latest SP.
Source was taken from CVS head today (7/10/2006).



Reproducible: Always

Comment 1

[Brendan Eich [:brendan]]

Not a problem with VS7.x and VS8, or with GCC.  Igor, any ideas?

/be

Comment 2

[Mike Moening]

There is also a warning on line 1230:
----------------
            arenaList->lastLimit = offset;
----------------
conversion from 'unsigned long ' to 'unsigned short ', possible loss of data

The lastLimit variable is defined as uint16 and offset is a jsuword
Just a little cleanup...

Comment 3

[Mike Moening]

If I change the line from:
    JS_STATIC_ASSERT(2 <= sizeof table->array[0]);

to:
    JS_STATIC(2 <= sizeof table->array[0]);

Then it compiles fine.  

I did notice that AddToPtrTable() is a static function.
However I don't know the difference between the two macros or the ramifications of this change.  Just thought I'd point this out.

Comment 4

[Brendan Eich [:brendan]]

(In reply to comment #3)
>     JS_STATIC(2 <= sizeof table->array[0]);

Did you mean JS_ASSERT?

/be

Comment 5

[Mike Moening]

Doh!

Yes I meant JS_ASSERT()  
Sorry for the confusion.

Comment 6

[Igor Bukanov]

(In reply to comment #1)
> Not a problem with VS7.x and VS8, or with GCC.  Igor, any ideas?

The strange thing is that it affects only DEBUG build when JS_STATIC_ASSERT is defined unconditionally. Does VC6 really can compile without DEBUG? And if this is a bug in VC6, then what happens if

 JS_STATIC_ASSERT(2 <= sizeof table->array[0]);

would be replaced by

 JS_STATIC_ASSERT(2 <= sizeof(void *));

?

Comment 7

[Mike Moening]

>The strange thing is that it affects only DEBUG build when JS_STATIC_ASSERT is
>defined unconditionally.

Asserts are defined to nothing in a release build, which is why it affects only DEBUG.

I've tried a bunch of things. All the following fail with the same error.
JS_STATIC_ASSERT(2 <= sizeof(void *));
JS_STATIC_ASSERT(2 <= 2);
JS_STATIC_ASSERT(1);

I guess that means JS_STATIC_ASSERT cannot be used in a static function.
All other static functions in this part of the code use JS_ASSERT() instead.

Brendan can you make this change?

Comment 8

[Igor Bukanov]

(In reply to comment #7)
> >The strange thing is that it affects only DEBUG build when JS_STATIC_ASSERT is
> >defined unconditionally.
> 
> Asserts are defined to nothing in a release build, which is why it affects only
> DEBUG.

No: JS_STATIC_ASSERT is defined unconditinally to *always* cause a compile-time error when the condition is violated, see http://lxr.mozilla.org/seamonkey/source/js/src/jsutil.h#65

> 
> I've tried a bunch of things. All the following fail with the same error.
> JS_STATIC_ASSERT(2 <= sizeof(void *));
> JS_STATIC_ASSERT(2 <= 2);
> JS_STATIC_ASSERT(1);
> 
> I guess that means JS_STATIC_ASSERT cannot be used in a static function.

No, it just means that VC6 can swallow typedef inside a function in this particular case. A trivial workaround would be to replace it by JS_ASSERT indeed . A better solution is to change JS_STATIC_ASSERT to take into account VC6 bug f possible.

> All other static functions in this part of the code use JS_ASSERT() instead.

It is because other conditions are not compile-time constants.

Comment 9

[Mike Moening]

Don't use Visual C++ 6.0 anymore... Closing bug.