tags 12142 notabug thanks On 08/05/2012 11:45 AM, Michał Górny wrote: > autoconf: 2.69 > automake: 1.12.2 > libtool: 2.4.2 > Also, which version of make are you using?
> Hello, > > I was writing a C++ library and I think I hit a pretty ugly bug within > automake. > What you describe below is not an Automake bug, but an unexpected interaction with the GNU make built-in rules. That is, GNU make contains (among other stuff) a built-in rule to compile programs from a C++ source files: <http://www.gnu.org/software/make/manual/make.html#Catalogue-of-Rules> and that is being somehow invoked as an unindented consequence of your declarations. More details below. > My library was structured like the following: > > - src/foo (the header file), > Why not simply using a more usual name like 'foo.h' for 'foo.hxx'? That would be unlikely to trigger unexpected problems in the first place ... > - src/foo.cxx (the code). > > These files assemble a library, let's call it libfoo.la. > > The problem is that every time I modify src/foo.cxx and call 'make', > automake > No, automake is doing nothing at this point. It's make that does the building and compiling, using both the instructions given in the Automake-generated Makefile and its own built-in rules. And it's one the latter that is wreaking havoc here. first (correctly) compiles the library, and then mistakenly > tries to compile and link it into a program src/foo, either effectively > overwriting or removing my header file, or failing early due to > missing dependency file. > I guess this doesn't happen if you run make with the '--no-builtin-rules' option. And in fact ... > What's interesting, 'make' calls not following src/foo.cxx changes work > correctly; just the one after modifying src/foo.cxx fails. > I've also prepared a git repository with the simple test case: > > git clone https://bitbucket.org/mgorny/automake-cxx-bug.git > cd automake-cxx-bug > autoreconf -vi > ./configure --disable-static > make # compiles fine > touch src/foo.cxx > make # fails > ... I've tried this out and verified that my diagnosis is correct. Bottom line: to avoid the issue, either rename the header file (the sanest thing to do IMO), or ensure make gets always run with the '--no-builtin-rules' option. Regards, Stefano
