How to find all files that constitute a translation unit in C++?

Question

I'm using a header only library and would like to include only the part of the library that I'm actually using.

If I include one of the library's headers how can I find all the other headers that are included by the library? Or phrased more generally: how can I find all files that make up a C++ translation unit? (I'm using g++ on Linux.)

Edit: Possible approaches with gcc (answers summary)

gcc -H produces output of the form:

... /usr/include/c++/4.6/cmath
.... /usr/include/math.h
..... /usr/include/x86_64-linux-gnu/bits/huge_val.h
..... /usr/include/x86_64-linux-gnu/bits/huge_valf.h

You have to filter out the system headers manually, though.

gcc -E gives you the raw preprocessor output:

# 390 "/usr/include/features.h" 2 3 4
# 38 "/usr/include/assert.h" 2 3 4
# 68 "/usr/include/assert.h" 3 4
extern "C" {    
extern void __assert_fail (__const char *__assertion, __const char *__file,
      unsigned int __line, __const char *__function)
      throw () __attribute__ ((__noreturn__));

You have to parse the linemarkers manually. See: http://gcc.gnu.org/onlinedocs/cpp/Preprocessor-Output.html

gcc -M produces a Make file for the given source file. The output looks as follows:

object.o: mylibrary/object.h /usr/include/c++/4.6/map \
 /usr/include/c++/4.6/bits/stl_tree.h \
 /usr/include/c++/4.6/bits/stl_algobase.h \
 /usr/include/c++/4.6/x86_64-linux-gnu/./bits/c++config.h \

possible duplicate of [Do you know tool building tree of include files in project\file?](http://stackoverflow.com/questions/1226044/do-you-know-tool-building-tree-of-include-files-in-project-file) — In silico, Feb 04 '13 at 09:54

score 4 · Accepted Answer · answered Feb 04 '13 at 10:16

4

I believe you're looking for gcc -H.

answered Feb 04 '13 at 10:16

Angew is no longer proud of SO

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score 3 · Answer 2 · answered Feb 04 '13 at 10:19

3

g++ -M somefile to get a makefile that has all files somefile included as dependencies for somefile.o.

g++ -MM somefile the same, but doesn't list system headers (e.g. anything in /usr/include or /usr/local/include).

What do you need this for? If it's for dependency tracking, the above should suffice. If you, on the other hand, want to do some crazy thing like "I include this header and that header includes this header, so I don't need to include it again" - don't. No, seriously. Don't.

answered Feb 04 '13 at 10:19

Cubic

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That only gives me the headers that are directly included. – Bernhard Kausler Feb 04 '13 at 10:30
@BernhardKausler Are you sure? Check again. It gives me all directly or indirectly included headers when I try it. – Cubic Feb 04 '13 at 10:35
1

@BernhardKausler `-M` gives all of the files the compiler reads to compile the source file. – James Kanze Feb 04 '13 at 10:37
@Cubic and James: You're right. I tried the -MM, that removed all headers of installed libraries. The -M option works as you say. – Bernhard Kausler Feb 04 '13 at 10:47

score 2 · Answer 3 · answered Feb 04 '13 at 09:54

2

You could obtain the preprocessed source using GCC's -E flag, then grep it for #include. I'm not aware of any other way for source files to find their way into a translation unit, so this should do the job.

answered Feb 04 '13 at 09:54

Lightness Races in Orbit

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Thanks for the hint! Unfortunately the "#include"s are gone after the preprocessor. But you can recover that information from the linemarkers inserted by the preprocessor. See: http://gcc.gnu.org/onlinedocs/cpp/Preprocessor-Output.html – Bernhard Kausler Feb 04 '13 at 10:25
Could you please update your answer accordingly so that I can accept it? :) – Bernhard Kausler Feb 04 '13 at 10:26

score 2 · Answer 4 · answered Feb 04 '13 at 10:14

With g++ (and most Unix compilers, I think), you can use -M. For other compilers, you'll need -E or /E, capture the output in a file, and post-process the file using your favorite scripting language. (I do this in my makefiles, to build the dependencies.)

How to find all files that constitute a translation unit in C++?

Edit: Possible approaches with gcc (answers summary)

4 Answers4