Debugging with GDB Manual HP WDB v6.3 (5900-2180, August 2012)

14.7.1 Fix and Continue compiler dependencies
Fix and Continue is supported only for PA-RISC on HP-UX 11.x with these compilers:
• HP C/ANSI C A.11.01.20, or later
• HP aC++ A.03.25, or later
• HP Fortran 90 2.4, or later
14.7.2 Fix and Continue restrictions
Fix and Continue has the following restrictions and behaviors:
• You cannot recompile code that has been optimized.
• You cannot add, delete, or reorder the local variables and parameters in a function currently
active on the stack.
• If you x a routine in a file that contains function pointers, those function pointers become invalid
and will likely cause the program to receive a SIGSEGV error if the pointers are used.
• You cannot change the type of a local variable, file static, global variable, or parameter of
a function.
• You cannot add any function calls that increase the size of the parameter area.
• You cannot change a local or file static or global variable to be a register variable, and
vice-versa.
• You cannot add an alloca() function to a frame that did not previously use alloca().
• New structure fields can be added at the end of a structure object, not in the middle of a
structure. New fields are only accessible by the modified files. Old structure fields remain
intact; no swapping of them is permitted.
• If the redefined function is in the call stack but not on the top of the call stack, the modified
code will not be executed when the execution resumes.
The modified function will be executed when it is called next time, or a rerun.
• Breakpoints in the original source file are moved to the modified fie. Breakpoints in the already
instantiated functions on the call stack in the original file are lost.
• If you change the name of a function and there was a breakpoint set to the old function, HP
WDB does not move the breakpoint to the new function. The old breakpoint is still valid.
• If the number of lines of the modified file is different from that of the original file, the placement
of breakpoints may not be correct.
• When the program resumes, the program counter is moved to the beginning of the same line
in the modified function. The program counter may be at the wrong line.
14.7.3 Using Fix and Continue
When HP WDB recompiles a fixed source file, it uses the same compiler and the same options
that were used to create the original executable. If the compiler generates any syntax errors or it
encounters any of the restrictions, HP WDB does not patch the changes into the executable image
being debugged.
After you successfully recompile the changes, HP WDB uses the fixed version of the code when
you use any of the execution commands such as step, run, or continue.
When you use the edit command, HP WDB then monitors any edited source files for additional
changes. After you enter the initial fix command, HP WDB checks for additional saved changes
to a source file each time you enter a program execution command. If a saved source file has been
112 HP-UX Configuration-Specific Information