Automake adds all kinds of subdirectories to -I, the list of directories
to be searched for header files. However, CLN's header files are not
supposed to be included without the cln/ subdirectory, so adding
-Iinclude/cln can lead to conflicts with other header files. (The
problem at hand was a conflict between CLN's string.h and the C
library's string.h).
Benefits:
1. If a header file gets modified, all dependent stuff gets rebuilt.
No need for 'make clean' after each header modification, no more
spurious errors, no more spurious rebuilds.
2. No more errors due to redefined preprocessor, compiler, and linker
FLAGS.
3. Build scripts don't try to build every *.cc file which happen to
lurk in the source directory.
Richard Kreckel
Alexei Sheplyakov