4.2 Specifying Linker Debugging Options

Summary information about library usage and loading can be obtained by passing additional options to the linker through the LD_OPTIONS environment variable. The compiler calls the linker with these options (and others it requires) when generating object binary files.

Using the compiler to call the linker is always recommended over calling the linker directly because many compiler options require specific linker options or library references, and linking without these could produce unpredictable results.

demo% setenv LD_OPTIONS ’–m -Dfiles’
demo% f95 -o myprog myprog.f
Example: Using LD_OPTIONS to create a load map:

Some linker options do have compiler command-line equivalents that can appear directly on the f95 command. These include -Bx, -dx, -G, -hname, -Rpath, and -ztext. See the f95(1) man pages or the Fortran User’s Guide for details.

More detailed examples and explanations of linker options and environment variables can be found in the Solaris Linker and Libraries Guide.

4.2.1 Generating a Load Map

The linker -m option generates a load map that displays library linking information. The routines linked during the building of the executable binary program are listed together with the libraries that they come from.

Example: Using –m to generate a load map:

demo% setenv LD_OPTIONS ’-m’
demo% f95 any.f
any.f:
 MAIN:
            LINK EDITOR MEMORY MAP

output    input    virtual
section   section  address         size

.interp            100d4          11
            .interp 100d4         11 (null)
.hash              100e8          2e8
            .hash    100e8        2e8 (null)
.dynsym            103d0          650
            .dynsym 103d0         650 (null)
.dynstr            10a20          366
            .dynstr 10a20         366 (null)
.text              10c90          1e70
.text              10c90    00 /opt/SUNWspro/lib/crti.o
.text              10c90    f4 /opt/SUNWspro/lib/crt1.o
.text              10d84    00 /opt/SUNWspro/lib/values-xi.o
.text              10d88    d20 sparse.o
...

4.2.2 Listing Other Information

Additional linker debugging features are available through the linker’s -Dkeyword option. A complete list can be displayed using -Dhelp.

Example: List linker debugging aid options using the -Dhelp option:

demo% ld -Dhelp
      …
debug: args           display input argument processing
debug: bindings       display symbol binding;
debug: detail         provide more information
debug: entry          display entrance criteria descriptors
      …
demo%

For example, the -Dfiles linker option lists all the files and libraries referenced during the link process:

demo% setenv LD_OPTIONS ’-Dfiles’
demo% f95 direct.f
direct.f:
 MAIN direct:
debug: file=/opt/SUNWspro/lib/crti.o  [ ET_REL ]
debug: file=/opt/SUNWspro/lib/crt1.o  [ ET_REL ]
debug: file=/opt/SUNWspro/lib/values–xi.o  [ ET_REL ]
debug: file=direct.o  [ ET_REL ]
debug: file=/opt/SUNWspro/lib/libM77.a  [ archive ]
debug: file=/opt/SUNWspro/lib/libF77.so  [ ET_DYN ]
debug: file=/opt/SUNWspro/lib/libsunmath.a  [ archive ]
      …

See the Linker and Libraries Guide for further information on these linker options.

4.2.3 Consistent Compiling and Linking

Ensuring a consistent choice of compiling and linking options is critical whenever compilation and linking are done in separate steps. Compiling any part of a program with some options requires linking with the same options. Also, a number of options require that all source files be compiled with that option, including the link step.

The option descriptions in the Fortran User’s Guide identify such options.

Example: Compiling sbr.f with -fast, compiling a C routine, and then linking in a separate step:

demo% f95 -c -fast sbr.f
demo% cc -c -fast simm.c
demo% f95 -fast sbr.o simm.o        link step; passes  -fast  to the linker