18.2.1.2 VxWorks Download

If you have connected to the VxWorks target and you want to debug an object that has not yet been loaded, you can use the No value for GDBN load command to download a file from Unix to VxWorks incrementally. The object file given as an argument to the load command is actually opened twice: first by the VxWorks target in order to download the code, then by No value for GDBN in order to read the symbol table. This can lead to problems if the current working directories on the two systems differ. If both systems have NFS mounted the same filesystems, you can avoid these problems by using absolute paths. Otherwise, it is simplest to set the working directory on both systems to the directory in which the object file resides, and then to reference the file by its name, without any path. For instance, a program ‘prog.o’ may reside in ‘vxpath/vw/demo/rdb’ in VxWorks and in ‘hostpath/vw/demo/rdb’ on the host. To load this program, type this on VxWorks:

-> cd "vxpath/vw/demo/rdb"

Then, in No value for GDBN, type:

(vxgdb) cd hostpath/vw/demo/rdb
(vxgdb) load prog.o

No value for GDBN displays a response similar to this:

Reading symbol data from wherever/vw/demo/rdb/prog.o... done.

You can also use the load command to reload an object module after editing and recompiling the corresponding source file. Note that this makes No value for GDBN delete all currently-defined breakpoints, auto-displays, and convenience variables, and to clear the value history. (This is necessary in order to preserve the integrity of debugger's data structures that reference the target system's symbol table.)