Hi again, Thanks a lot for your answer. Your response surprised me, and you are right. It appears that I over-simplified my problem for this mailing-list, and removed the important bit : the fact that I am using -Werror. Now, if you run "g++ -MM -MG -Werror a.h", you will get: a.h:1:9: error: #pragma once in main file Since I am not willing to change the compilation flags that my users provide, I am just adding a -Wno-error flag at the end, which seems to work fine. Thanks again for the help, -- Remi 2011/4/8 Axel Freyn <axel-freyn@xxxxxx>: > Hi Rémi > On Fri, Apr 08, 2011 at 02:10:32PM +0200, Rémi Delmas wrote: >> Hello, >> >> I need to compute the file dependencies for C++ source and header >> files. Using the -MM option of gcc, here is how I proceed today: >> >> For example, if I need to get the dependencies for main.cpp and >> main.hpp, I would execute : >> >> >g++ -x c++ -MM -Iincludepath main.cpp main.hpp >> main.o: main.cpp main.hpp includepath/include2.hpp >> main.o: main.hpp includepath/include2.hpp >> >> I then parse the output to get my result with minimal effort (I ignore >> the .o file, and the remainder of the line is simply the original >> source file followed by the list of its dependencies). >> >> My problem is that the -MM option of gcc is not meant to be used with >> header files, and seems to choke on header-only pragmas such as >> "#pragma once". I have been looking at an option to ignore pragmas, >> with no success. >> >> Could anyone either provide me with a way to ignore unwanted pragmas, >> or else with a idea on how to achieve the desired result? >> >> Thanks a lot in advance. CC'ing me in the reply would be very much >> appreciated. Since this is the first time I post on that list, please >> redirect me to a more appropriate list if needed. > > For me, this works as expected. With the two files: > test.cc: > #include "a.h" > #include "b.h" > a.h: > #pragma once > #include "c.h" > > I obtain (this is g++ version 4.1.2): > > g++ -MM -MG test.cc > test.o: test.cc a.h c.h b.h > > g++ -MM -MG a.h > a.o: a.h c.h > > which seems to be fine. The "-MG" just assumes missing files to be > auto-generated (here: b.h and c.h) > > Did I misunderstand your problem? > > Another solution to your problem might be the use of "makedepend", which > has nothing to do with gcc (at least to my knowledge), but which is > designed to generate such header-dependencies in a most-efficient way > (especially if you have really large projects...) > > Axel >
