Using Makefile to add new source code files to Postgresql

Question

I'm working on adding some functionality to the storage manager module in Postgresql. I have added few source files already to the smgr folder, and I was able to have the Make system includes them by adding their names to the OBJS list in the Makefile inside the smgr folder. (i.e. When I add A.c, I would add A.o to the OBJS list).

That was working fine. Now I'm trying to add a new file hdfs_test.c to the project. The problem with this file is that it requires some extra directives in its compilation command (-I and -L directives).

The gcc command is:

gcc hdfs_test.c -I/HDFS_HOME/hdfs/src/c++/libhdfs -I/usr/lib/jvm/default-java/include -L/HDFS_HOME/hdfs/src/c++/libhdfs -L/HDFS_HOME/build/c++/Linux-i386-32/lib -L/usr/lib/jvm/default-java/jre/lib/i386/server -ljvm -lhdfs -o hdfs_test

Therefore, simply adding hdfs_test.o to the OBJS list doesn't work. I tried editing the Makefile to look like this:

OBJS = md.o smgr.o smgrtype.o A.o B.o hdfs_test.o

MyRule1 : hdfs_test.c
gcc tati.c -c -I/diskless/taljab1/Workspace/HDFS_Append/hdfs/src/c++/libhdfs -I/usr/lib/jvm/default-java/include -L/diskless/taljab1/Workspace/HDFS_Append/hdfs/src/c++/libhdfs -L/diskless/taljab1/Workspace/HDFS_Append/build/c++/Linux-i386-32/lib -L/usr/lib/jvm/default-java/jre/lib/i386/server -ljvm -lhdfs

but it didn't work out, and I kept getting errors message of the Make trying to compile hdfs_test.c without including the directives.

How do I enforce the Make to include my compilation directives for hdfs_test.c ?

Thanks

Craig Ringer Craig Ringer · Accepted Answer · 2011-12-04T13:00:42

You don't need to pass -l and -L at compile time, only at link time. At compile time only -I (include path) directives are required to help the compiler find any extra headers.

You should compile your source file to a .o file, same as all the others. Then add the -L and -l directives to the link command line when the linker is invoked to create the postgres executable. That means all you need to edit in src/backend/storage/smgr/Makefile is the OBJS line to add your output object, as you've already done below. Remove your custom rule, it's unnecessary as well as incorrect.

Just add your extra libraries to the $(LIBS) make variable and add your -L paths to $(LDFLAGS) via src/Makefile.global. src/Makefile.global is generated by configure from src/Makefile.global.in so you actually need to modify configure's behavior to add your includes, library paths and libraries. Don't edit configure directly either; edit configure.in and re-generate it with autoconf.

Yes, GNU Autotools is sometimes referred to as autohell for a reason. It's a bit ... interesting ... to work with sometimes, and there can be a lot of indirection involved in doing simple things.

Using Makefile to add new source code files to Postgresql

1 Answers