B Link Script Details

The link scripts firstly have to create a subroutine, DTASK_APPLIC, which is called by the ADAM fixed part and in turn calls the user’s top-level routine. The difference between alink and ilink is just that the template DTASK_APPLIC for alink contains a call to close down the parameter system after each invocation of the task unless the environment variable ADAM_TASK_TYPE is set to ‘I’.

If the user’s main routine is written in C, a temporary routine, DTASK_WRAP is created as a Fortran-callable wrapper for the user’s routine. DTASK_APPLIC will call DTASK_WRAP, which in turn calls the user’s routine.

During installation (as part of the DTASK library in the PCS package), the actual compile/link command within alink/ilink is edited depending upon the platform and setting of various environment variables. The template command is:

Notes:

• F77 is replaced by whatever the FC environment variable is when alink/ilink is installed.
• Any C source files specified will be compiled separately and linked in the above Fortran command. The C compiler command used will be of the form:
    % CC -c $CFLAGS $CARGS -I/star/include

  where:

  CC

  is replaced by the CC environment variable when alink/ilink script is installed.

  $CFLAGS

  is the value of the CFLAGS environment variable when alink/ilink is invoked.

  $CARGS

  is any C files or -I or -D arguments on the alink/ilink command line, plus, if the main routine is C, dtask_wrap.c

• $EXENAME is the basename of the prog_module argument of alink/ilink with any .f, .c or .o suffix removed.
• Environment variable FFLAGS may be used to specify any options which must be included at the start of the command line.
• $XDBX is set to -g if the -xdbx argument is given.
• $ALINK_FLAGS1 may be set to determine the type of linking required. For instance:
    % setenv ALINK_FLAGS1 -L/star/share

  would cause the linker to find the Starlink shared libraries (on platforms where they are installed), thus producing a dynamically linked executable.

• $ARGS is the prog_module argument (with .o appended if the original extension was not .f, .c or .o) or $EXENAME.o dtask_wrap.o if the main routine was in C, followed by the remaining arguments unchanged except that any .c file extensions are replaced by .o.
• To speed up the link, pkg_link_adam scripts are only used selectively. dtask_link_adam refers to DTASK, TASK and ERR libraries directly then invokes subpar_link_adam which references the necessary libraries directly, apart from HDS, HLP and PSX whose link_adam scripts are invoked.
• ALINK_FLAGS2 may be useful in controlling the way system libraries are accessed.
• Additional system libraries A platform-dependent list of required system libraries which are not searched automatically is added to alink/ilink at installation time.
• Other adjustments are made during installation if PCS is not being installed in /star. In particular, a -L option is added to include the newly installed libraries before those in /star/lib. Similarly with -I options in the C compilation.

The -xdbx argument is provided to overcome some awkward problems which can arise when debugging ADAM applications. Usually it is sufficient to include -g in the arguments of alink/ilink but sometimes, notably when using xdbx and ups on SunOS, the debuggers do not behave sensibly if required source files are missing so the -xdbx argument should be used instead. The effects of the argument are:

• A dummy source file for dtask_main, the main routine of every ADAM task, is created in the working directory. The file contains an explanatory message to the user and the name of the user’s top-level subroutine (which may be helpful in selecting a breakpoint).
• The source file of DTASK_APPLIC is not deleted from the working directory.
• -g is inserted in the compile/link command.