-fdebug-prefix-map sometimes randomly has no effect?

[Dave Gittins]

Hi,

I have been using -fdebug-prefix-map successfully recently, while
compiling C++ on Centos 6 boxes. I just hit a strange stumbling block
though - sometimes, under conditions I can't quite pin down, it just
doesn't work. I can compile an object file and look at the output with
dwarfdump and see that the prefix maps have been applied, and then
make an apparently innocent code change, compile again, and find that
none of the maps have been applied.

I have seen this behaviour with both gcc 4.4.0 and 4.4.7.

I tried to whittle the code down to a small example I can pass along,
but I get to a point where it starts working fine while the code is
still quite large. So I don't have an example I can share yet, sorry.
The code in question is including various boost headers if that helps.

Dave