[cfe-dev] PCHReader: FileIDs in ParseLineTable()

[Zhongxing Xu]

2009/5/23 Douglas Gregor <dgregor at apple.com>:
>
> On May 22, 2009, at 2:00 AM, Zhongxing Xu wrote:
>>
>> The FileIDs in ParseLineTable() of PCHReader.cpp probably is not
>> needed, since we emit filenames in their ID order, and read filenames
>> in the same order. The file IDs remains unchanged. In practice we are
>> always creating identity mapping from x to x.
>
>
> I actually did think about this when I added the FileIDs map, and it was
> that "probably" that made me write it this way. I'm fairly certain that we
> don't need the map. However, since #line directives are so rare in headers,
> and the failure mode is likely to be weird---diagnostics showing up in the
> wrong place---I decided that it was better to be defensive here, since it
> won't cost us much. Plus, if we ever get to the point of loading multiple
> PCH (or PCH-like) files, we'll need this map.

Ah yeah, multiple PCH is good reason for this.

>
>        - Doug
>