I'm posting this and then answering myself to document the issue for others.
I am using the TI CC2650 Launchpad with the Simplelink BLE stack. The project I compile and run is Project Zero (with edited code and additional profiles).
I want to place breakpoints in some functions inside the profile. For most of them i can't! When I look in the disassembly while debugging, I see that symbols are not available.
The only places I can place breakpoints are in main.c or inside callbacks.
How do I place breakpoints elsewhere? Where are my symbols?
So the deal was this - the functions I was trying to place breakpoints in were static functions, internal to the C modules containing them. Out of those, most were only used once in the code. So the compiler inlined them!
So in order to achieve debugging for these functions, one has to disable compiler optimizations. That disables inlining, and causes the symbols for those functions to generate.
Related
This might be a newbie question, but I am going crazy already haha.
symptom
I am having an issue with the lpcxpresso54102 Dev Board, where I am not able to access main.c during debug session, but if I check on the disassembly window I can see the main file, instruction set and actually the project works and I am able to set breakpoints through disassembly. disassembly_data
symptom
If I place a break point on main.c, when I start the debug session, my breakpoint is replaced by a circle with a exclamation point inside the circle. Browsing through ARM dev QA site, I was able to find that this issue is related to
NO CODE AT BREAKPOINT: A breakpoint could not be set because there is no code generated for this source code line. Compiler or linker optimization can remove unnecessary source code.
ARM_DEV_QA
NOTE: optimization config. was modified from original project to 0 optimization level.
symptom
Once I enabled the option for debug information on the target configuration, the file "startup_LPC54102_cm4.s", the cursor was actually going trough the file and eventually reaching the infinite loop used to toggle the led on the board.
NOTE: This file is the example code from the SDK example lib from NXP (blinky), but all the other examples behave the same in UVision, but if I tried on MCUXpresso IDE the debug session works just fine.
Also I checked the linker files and they seem to be ok.
I changed the configuration on the target of Uvision enabling the output info and also changing the optimization to level 0, checked the compiler control string on C/C++ tab and it seems that all the files path and controls are there (no completely sure though). I tried with external and internal debug HW, same behavior.
https://webassembly.studio/ allows inspection of WebAssembly (WASM) files and the corresponding SpiderMonkey-generated x86 code. I'd like to similarly inspect instructions generated by V8's WASM compilers (Liftoff and TurboFan).
I'm entirely unfamiliar with V8's codebase/API (I compiled & linked it and followed some tutorials, though). There seems to be a v8::CompiledWasmModule class available, but it does not seem to expose access to generated x86/x64 instructions by either Liftoff or TurboFan.
WebAssembly - adding a new opcode describes the process of adding a WASM opcode to V8. Seemingly appropriate functions for WASM compilation/execution are available in the mentioned classes. Though, these seem rather deeply layered within the V8 codebase and would be difficult to access were I to link V8 as a library. Also, I'm unsure if this corresponds to Liftoff or TurboFan.
Could anybody familiar with the V8 codebase give me some pointers as to how I can access Liftoff and/or TurboFan's WebAssembly compilation module, as to obtain x86/x64 code?
To inspect generated code, you can run the d8 shell with the --print-wasm-code flag. You'll need either a debug build, or a release build with the v8_enable_disassembler = true GN arg.
There's no existing way to retrieve generated code via V8's API; so if that's what you want, then you'd have to add it. Keep in mind that V8 is not designed to be a standalone compiler, which means generated code assumes that it's going to run "inside V8", so if you wanted to use it for anything else, you'd have to make significant modifications.
I compiled my application with debug symbols using clang. When attaching to the application using lldb and stepping into, for example, __cxa_throw, I don't see the source code of libc++abi.dylib. What am I doing wrong?
You do get some debug information for the STL, because a lot of the STL code is in header files that get compiled into your application. But you don't have debug information for the code that is actually compiled into libc++abi.dylib, since Apple doesn't distribute dSYM's for system libraries. __cxa_throw is actually a function in the library.
As a separate issue, because most people don't actually want to step into STL code, lldb has a setting:
(lldb) set show target.process.thread.step-avoid-regexp
target.process.thread.step-avoid-regexp (regex) = ^[^ ]+ std::|^std::
that will cause stepping to artificially step over code from the STL. You can undo this by setting that value to "". That will get you into the inlined code when stepping.
I am using Visual Studio 2010 to debug an application mostly written in C. Normally, I can attach the debugger just fine, but I am running in to some problems when I link in a library written in C++ / CLI.
If I compile the library with the /clr flag (which I will eventually have to do for this as of yet unwritten library) then I lose all ability to debug the entire C application, even the parts that have nothing to do with the library calls. I get the empty circle with the yellow triangle and exclamation mark where a red break point circle ought to be. Hovering over it gives me only a tool tip that says "The breakpoint will not currently be hit. No executable code is associated with this line. Possible causes include: conditional compilation or compiler optimizations."
Then if I link with the exact same library compiled without the /clr flag, I am again able to debug my application.
I understand that visual studio will not likely be able to debug the library written in C++ / CLI, and that is OK. I just want to keep the ability to debug the rest of the application and at least see the results of my calls to the external library.
Another complicating factor is that this project is not being built by visual studio. It is compiled using an external make system that uses cl, so I can customize any commands that need to be issued to the compiler that way.
Does anyone know why I can't currently debug the libraries the way I want to? Any advice for how I can?
You have to select the kind of debugger when you attach. Note the "Attach to" label in the dialog. Press the Select button and tick "Native" to get support for debugging native code. The DLL also needs to be loaded before any of your breakpoints can hit. If you are not sure whether or not that was done then look in the Debug > Windows > Modules debugger window to see loaded DLLs. The breakpoint indicator turns from hollow to solid red as soon as the debugger saw the DLL load and armed the breakpoint.
Debugging C++/CLI is otherwise supported, you can tick both the "Managed" and "Native" checkboxes. And set breakpoints in either kind of code. The only thing not supported is single-stepping from managed to native code and back. A mode-switch is required to activate the correct debugging engine, that requires code to hit a breakpoint.
And consider the Debug options in your native project, you can specify an EXE to start. So that you can simply press F5 to start debugging and skip the attach hassle.
It might also have to do with the Debugger Type!
(but that depends on your specific building configuration about which I do not know enough)
If any of your projects is complied with Common Language Runtime Support (/clr) you should set the Debugger Type in your startup project to "Mixed", since the default setting "Auto" might fail!
Imagine, you have two projects:
1) A non-CLR C++ project, which is your startup project that generates some .exe file.
2) A C++ project, that generates mylibrary.dll, which is compiled with Common Language Runtime Support, because it uses some managed code. The .exe from the first project calls mylibrary.dll.
If you start the first project with Debugger Type set to its default value "Auto", you'll be able to debug into the first project, but not into the second one. The debugger selector does not realize that you will be calling a CLR-library.
So set Project Properties -> Configuration Properties -> Debugging -> Debugger Type to "Mixed"!
With g++ with -g option, I can use gdb for debugging purposes.
What's the equivalent to this option with Visual Studio 2010 cl.exe compiler?
This page has different libraries (debug/release) for linking.
If I compile with debugging option with cl.exe, do I have to use the corresponding library linking options (/MD/MT vs /MDd/MTd)?
There are a few separate pieces to this question: how to tell the compiler/linker to generate and preserve "debug information" (mapping between source code and object code), how to tell the compiler to compile the code differently to make debugging easier (think of assert() and #ifdef _DEBUG), and whether the precompiled libraries you link into your project include debugging information.
-Zi (flag to the CL compiler to tell it to generate debug information) is the equivalent of gcc's -g flag.
(There are other forms of the -Z option: -ZI if you want the "edit and continue" support in the Visual Studio IDE, but if you're using the IDE you're probably using its interface to the compiler settings instead of manipulating them directly, and -Z7 if you want the old CodeView-format debug information; whenever I've invoked CL directly it's always been -Zi that I wanted.)
Note that using the -Zi (or -ZI) option will generate a .pdb file per directory, usually, but when you link code together, it may have come from .obj files represented in different .pdb files, and you also want to combine those separate .pdb files into a master one representing the code you linked together -- this is what the -debug switch for the linker is for.
Also note: this may sound counterintuitive, but always use -Zi (for CL) and -debug (for link.exe). Even for code you're going to release. It doesn't increase the size of your executable, or give away secrets to your customers, since the debug information goes in a separate .pdb file (which you won't ship to customers). If there's any chance you're ever going to have to debug it, you're going to want the .pdb. (-Zi isn't even incompatible with optimizations, though -ZI is. So you might want to compile your "debug" builds with -ZI, and your "release" builds with "-Zi -O2".)
As for the libraries: you don't strictly need to match the debug/release property of the C runtime library with whether your code includes debugging information, but it's usually a good idea -- if you're going to debug the project you want to be able to debug all of it, and if you're not going to debug it you don't need the extra weight. Using debug/release versions of a given library won't affect whether it has debug symbols available (hopefully, if whoever compiled the library understood the point I made in the previous paragraph), but it will affect things like assert and extra #ifdef _DEBUG code in that library.
This goes for all libraries you link with, but especially for the C runtime library -- Microsoft added extra error-detection code to malloc() and free(). So if anything in your project is using the debug flavor of the CRT library, all of it should be.
The /M options (/MTd and /MDd) are weird and magic, in my opinion -- they're just aliases for a complicated set of other stuff going on behind the scenes. Take /MDd for example, documented to "Defines _DEBUG, _MT, and _DLL and causes your application to use the debug multithread- and DLL-specific version of the run-time library. It also causes the compiler to place the library name MSVCRTD.lib into the .obj file." Here, it's affecting both the preprocessor (defining _DEBUG and some other preprocessor symbols) and the linker (it actually puts a #pragma comment(linker) in your source code). If you care about what's going on and don't understand it, this can cause real problems -- I've seen a lot of projects that don't use the IDE get bogged down in warnings about both msvcrt.lib and msvcrtd.lib being linked in, etc. By the time you understand how to use these (/M options) safely, you don't really need them any more! I prefer to make things explicit: specify "-D _DEBUG" directly where I need it, specify which libraries to link with explicitly (and use -nodefaultlib), and then the /M options aren't needed.
You're looking for one of the debug information generation options (/Z7, /Zi or /ZI).
If you use one of those, you should also pass the /DEBUG option to the linker.
You will also need to link against the debug version of the runtime libraries (/MDd or /MTd). This is important because these versions are different from their release counterparts (e.g. their memory allocations routines are not compatible).