debug: add interactive debug mode #203
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When an inner function invoked exit() in a ucode > native > ucode call stack situation, the VM did end up with an empty callframe stack after the native function returned, leading to subsequent invalid memory accesses. Properly deal with situation similar to how we also check for an empty call stack after processing I_RETURN and additionally translate the current exception type to a status return value. Signed-off-by: Jo-Philipp Wich <[email protected]>
Add missing definition for the SIGWINCH signal number in order to allow ucode programs to subscribe to terminal size change signals. Signed-off-by: Jo-Philipp Wich <[email protected]>
Use a two byte structure to encode { byte offset, insns count } offset
info tuples and introduce additional flags plus related api functions to
encode statement start- and end boundaries in offsetinfo.
The new encoding format more than halves the required memory footprint
in many cases, especially for whitespace- and comment heavy sources.
Signed-off-by: Jo-Philipp Wich <[email protected]>
Utilize the new chunk offset info facilities to encode the start and end offsets of logical statements in the offset information vector of the debug data area. This information can be used later by debuggers to step through logical statements instead of single instructions. Signed-off-by: Jo-Philipp Wich <[email protected]>
Introduce low level facilities for registering breakpoints in the running VM context. The breakpoint primitives allow invoking provided callback functions when the VM reaches an associated instruction address. This functionality provides the foundation for building more thorough interactive debug functionality on top. Signed-off-by: Jo-Philipp Wich <[email protected]>
Publicly export the instruction format table in order to make it useable for libucode.so users, such as dynamically loaded debug libraries. Signed-off-by: Jo-Philipp Wich <[email protected]>
When additional ucode scripts are loaded through require() or similar means, and the required code invokes exit(), the VM will clear the stack before returning, so we must ensure that the stack size matches our expectation before we're trying to pop values from it after returning from require. Signed-off-by: Jo-Philipp Wich <[email protected]>
Implement an interactive command line debugger within the debug module which can be started by invoking the `debugger()` function. The debugger offers common features such as the ability to set breakpoints, stepping through commands, examining call stacks and variables as well as byte code disassembly source code highlighting. Signed-off-by: Jo-Philipp Wich <[email protected]>
Introduce a new command line switch `-x` which loads the debug module and launches the given program or expression within the interactive debugger. Signed-off-by: Jo-Philipp Wich <[email protected]>
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Introduce a new interactive debug cli which can be started by invoking the ucode interpreter with the
-xflag.The main debugger functionality resides in the debug library while the cli frontend just gains some minimal amount of code to load and instantiate the debug library when the
-xoption is passed.As a precondition for the new debug functionality, the ucode VM has been extended with low level breakpoint support.