This tool takes a list of C or C++ sourcefiles and generates a report on which #includes can be omitted
from them; also, what standard inclusions may be required for portability. The test, for each foo.c or
foo.cc or foo.cpp, is simply whether "rm foo.o; make foo.o" returns a zero status (but the build command
may be overridden).
Exception: Under cmake, foo.o is a phony target. Therefore, when a "CMakeList.txt" is detected, "make
clean" is done rather than "rm foo.o".
Optionally, with the -r switch, the unneeded headers are removed from the sourcefiles. Don't use this
option unless you have your sourcefiles safely under version control and can revert!
If a sourcefile argument is a directory, the report is generated on all source files beneath it.
Subdirectories beginning with a dot are assumed to be repository directories for version-control systems
and ignored. If no arguments are given, the program runs as if the name of the current directory had been
passed to it.
Inclusions within the scope of #if/#ifdef/#else/#endif directives are left alone, because trying to
reason about potential combinations of -D and U options would be too complicated and prone to weird
errors. One exception: headers protected only by S_SPLINT_S, the conditional for blocking scanning by the
static analysis tool splint(1), are scanned normally.
The tool will also emit warnings about duplicate inclusions, and inclusions required for portability but
not present.
It is recommended that you arrange to compile with options that will stop the compiler on warnings when
using this tool; otherwise it will report headers that only declare prototypes and return types (and thus
throw only warnings) as being not required. Under gcc the compiler options to accomplish this are -Werror
-Wfatal-errors. If your makefile follows normal conventions, running with -m"makeCFLAGS='-Werror-Wfatal-errors'%s" may do the right thing; you can check this by running with -v -v -v to see what
compilation commands are actually emitted.
On each test compile, the original sourcefile is moved to a name with an .orig suffix and restored on
interrupt or after processing with its original timestamp, unless the -r option was given and headers
removed.
If the -b option is given, it tells the program that generated .o files live in a file tree parallel to
the source tree but rooted at the specified argument. If the argument is a relative path, it is
interpreted relative to the directory in which deheader is run.
If the first test compilation from the top-level directory fails, deheader descends into the subdirectory
of the source file and retries compiling inside there.
At verbosity level 0, only messages indicating removable headers are issued. At verbosity 1, test
compilations are timed and progress indicated with a twirling-baton prompt. At verbosity level 2, you get
verbose progress messages on the analysis. At verbosity level 3, you see the output from the make and
compilation commands.
If the -q (--quiet) option flag was not set, the last line of the output will be a statistical summary.
Running deheader will leave a lot of binaries in your directory that were compiled in ways possibly not
invoked by your normal build process. Running "make clean" afterwards (or the equivalent under whatever
build system you are using) is strongly recommended.
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