Patch for %E formatting for C

[Gabriel Dos Reis]

"Joseph S. Myers" <jsm@polyomino.org.uk> writes:

| On Sun, 2 Oct 2004, Gabriel Dos Reis wrote:
| 
| > that point C++ front-end would cease to pass plain IDENTIFIER_NODE
| > around -- I expect it will wrap them in something that is an
| > expression, otherwise the whole front-end will break :-). 
| > And I also expect that, at that point, th C front-end wouold improve too.
| 
| It has already improved in some places where identifiers could be confused 
| with other trees (for example, declarators now wrap the identifier in a 
| separate structure rather than having the IDENTIFIER_NODE itself represent 
| an identifier as a declarator).  There is indeed plenty more to do.
| 
| > One could argue that the cases where the C front-end would need to
| > pass IDENTIFIER_NODE to the pretty-printer should be inexistant, and
| > it does then it contains a bug.  If an IDENTIFIER_NODE is the name of
| > a _DECL, then pass that decl, not the identifier.
| 
| There are many cases where %qs is presently used with IDENTIFIER_POINTER, 
| where there is an identifier that does not correspond to a DECL.  For 
| example, all the instances of
| 
|       warning ("%qs attribute ignored", IDENTIFIER_POINTER (name));
| 
| or the error
| 
|       error ("label %qs referenced outside of any function",
|              IDENTIFIER_POINTER (name));

I think that poking at IDENTIFIER_POINTER is a bug, but that is the
point the C front-end is currently written.  The C++ front-end has
none of those (and I missed one, then that is a bug :-)

A label is a decl (LABEL_DECL) so it should have been used with %E,
just like any other _DECL in such contexts.  It seems that most of
those cases  where " a clear use of %I" is advocated, there is a
misuse of IDENTIFIER_POINTER in the first place; those should have
referenced the real entity. 

| - so there is a clear use for %qI for such cases, while others should 
| become %qD, if a DECL can be identified (even if presently the name rather 

Again, %qD does not does type the argument being passed, but *request*
a particular form printing; just like when you way %qE, you're requesting
pretty-printing as expression.  The formats control how the nodes are
displayed.

| than the DECL is being passed to the relevant function).  At the same time 
| there is a clear use for %E for genuine expressions, and probably many C 
| front end diagnostics could be improved by its use.

Agreed.

-- Gaby