[Bug pch/14137] [pch] ICE in cgraph_finalize_compilation_unit, at cgraphunit.c:407

["bangerth at dealii dot org" <gcc-bugzilla@gcc.gnu.org>]

------- Additional Comments From bangerth at dealii dot org  2004-03-30 23:25 -------
In my view, if compilation time is a problem, then  
a) the project is big, 
b) we are talking about regular builds, not ones where someone 
   is playing with compiler options, and 
b) very likely people are using a makefile to build things. 
It seems very likely that within a Makefile, the number of different 
combinations of flags is relatively small (say: 2, one for debug, one 
for optimized builds), and in this case it is reasonable to ask them 
that they generate one pch file per set of flags. After all, we support 
this, by putting multiple pch files into one directory. 
 
I consider simply requiring the user to use the exact same combination 
of flags as an absolutely acceptable requirement and am not expecting 
that we get many bug reports. On the other hand, if we get reports about 
incorrect code generation due to problems with PCH, this is going to be 
significantly worse. Please also keep in mind here that PCH bugs are us 
bugmasters' worst nightmares, since they often come in huge chunks, 
involve not only a single preprocessed file but a large collection of header 
files, may involve different compilation flags for different parts of the 
build, etc. PCH bugs have been very resistant to our efforts in the past, 
and have most often been analysed by the people who know how PCH is  
implemented, rather than by bugzilla people. I therefore very strongly 
urge you to go the safe route and only allow mixing compilation flags for 
PCH generation and PCH use if we are _absolutely_ (double-checked, verifiably) 
sure that this is safe! 
 
W. 
 

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14137