[cfe-dev] Problem in locations

[Abramo Bagnara]

Chris Lattner ha scritto:
> 
> On Aug 12, 2009, at 8:04 AM, Abramo Bagnara wrote:
> 
>> If I try to compile the attached program I get:
>>
>> $ ~/llvm/Debug/bin/clang-cc -pedantic -std=c89 z.c
>> z.c:2:9: warning: variable declaration in for loop is a C99-specific
>> feature
>>  for ( \
>>        ^
>> 1 diagnostic generated.
>>
>> The token start is not indicated in the position of the "i" of "int" but
>> in the previous line and the token length is set to 5.
>>
>> Is it intentional or it is a bug?
>>
>> IMHO to have a leading \newline as part of the token confuses the
>> diagnostic without benefits.
>> int p() {
>>  for ( \
>> int i = 0; i < 10; ++i)
>>    ;
>>  return 0;
>> }
> 
> That is perhaps not the best quality of implementation for the
> diagnostic, but it is intended.  You're hitting issues that are due to
> the phases of translation in C.  The first phase removes escaped
> newlines (which, as a gnu extension, can be followed by horizontal
> whitespace... urg) and trigraphs.  Because the lexer fully integrates
> the various phases of translation, a source location for a token returns
> the first byte of the file that is part of that token.  In this case, it
> is the escaped newline.

Why the escaped newline is not considered the last part of the whitespace?