Re: BUG #13898: ecpg complains on nested comments in /usr/pgsql-9.4/include/informix/esql/datetime.h

On 2016-02-01 13:16:20 +0100, Michael Meskes wrote:
> > and ends on an ordinary line.  I am not sure what the C standard says
> > about such cases, but I can certainly imagine that some tools might not
> > be very happy with that.
>=20
> We/I have to figure out what the standard says, because if it allows
> these comments, the lexer itself has to be fixed to work correctly
> instead of just fixing the header files.

The relevant translation phases are 3 and 4 according to the C standard
(section 5.1.1.2 in C11):

| 3. The source file is decomposed into preprocessing tokens7) and
|    sequences of white-space characters (including comments). A source
|    file shall not end in a partial preprocessing token or in a partial
|    comment. Each comment is replaced by one space character. New-line
|    characters are retained. Whether each nonempty sequence of
|    white-space characters other than new-line is retained or replaced
|    by one space character is implementation-defined.
|
| 4. Preprocessing directives are executed, macro invocations are
|    expanded, and _Pragma unary operator expressions are executed. If a
|    character sequence that matches the syntax of a universal character
|    name is produced by token concatenation (6.10.3.3), the behavior is
|    undefined. A #include preprocessing directive causes the named
|    header or source file to be processed from phase 1 through phase 4,
|    recursively. All preprocessing directives are then deleted.

Comments are replaced with whitespace in phase 3, preprocessing
directives are are only considered in phase 4. So code like=20

----------------------------------------------------------------------------
#ifndef _ECPGLIB_H             /* source created by ecpg which defines thes=
e=E2=90=A4
                                * symbols */=E2=90=A4
----------------------------------------------------------------------------

is valid C and should be exactly equivalent to

----------------------------------------------------------------------------
#ifndef _ECPGLIB_H              =E2=90=A4
=E2=90=A4
----------------------------------------------------------------------------

(=E2=90=A4 denotes a newline character here)

    hp

--=20
   _  | Peter J. Holzer    | I want to forget all about both belts and
|_|_) |                    | suspenders; instead, I want to buy pants=20
| |   | hjp@hjp.at         | that actually fit.
__/   | http://www.hjp.at/ |   -- http://noncombatant.org/