Hi, Marek,

Thanks a lot for the information. 

Really helpful.

Qing

> On Oct 20, 2021, at 12:57 PM, Marek Polacek <pola...@redhat.com> wrote:
> 
> On Wed, Oct 20, 2021 at 03:49:09PM +0000, Qing Zhao via Gcc-patches wrote:
>> Hi,
>> 
>> In GCC, there are many utility routines for reporting error, warning, or 
>> information, for example:
>> 
>> warning (0, "weak declaration of %q+D not supported", decl);
>> warning_at (stmtloc, OPT_Wmaybe_uninitialized,  "%qE may be used 
>> uninitialized", ptr));
>> inform (loc, "in a call to %qT declared with " "attribute %<%s%>", fntype, 
>> access_str);
>> error ("%qD is unavailable: %s", node, (const char *) msg);
>> 
>> There are format-strings inside them, “%q+D”, “%qE”, “%qT”, “%qD”, etc, 
>> where can I find a doc for the details of
>> These format-strings? Or which source files I should read to understand the 
>> details?
> 
> You can take a look at cp/error.c:
> 
> /* Called from output_format -- during diagnostic message processing --
>   to handle C++ specific format specifier with the following meanings:
>   %A   function argument-list.
>   %C   tree code.
>   %D   declaration.
>   %E   expression.
>   %F   function declaration.
>   %H   type difference (from).
>   %I   type difference (to).
>   %L   language as used in extern "lang".
>   %O   binary operator.
>   %P   function parameter whose position is indicated by an integer.
>   %Q   assignment operator.
>   %S   substitution (template + args)
>   %T   type.
>   %V   cv-qualifier.
>   %X   exception-specification.  */
> static bool 
> cp_printer (pretty_printer *pp, text_info *text, const char *spec,
> 
> or c/c-objc-common.c:
> 
> /* Called during diagnostic message formatting process to print a
>   source-level entity onto BUFFER.  The meaning of the format specifiers
>   is as follows:
>   %D: a general decl,
>   %E: an identifier or expression,
>   %F: a function declaration,
>   %T: a type.
>   %V: a list of type qualifiers from a tree.
>   %v: an explicit list of type qualifiers
>   %#v: an explicit list of type qualifiers of a function type.
> 
>   Please notice when called, the `%' part was already skipped by the
>   diagnostic machinery.  */
> static bool
> c_tree_printer (pretty_printer *pp, text_info *text, const char *spec,
> 
> Marek
> 

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