I am running gdb 10.1.90.20210103-git and gcc/g++ 10.2.1 20210110 on x86-64 Debian 11. My IDE is Codelite, which uses the manual rather than the machine interface to gdb, and enables me to type commands directly to gdb, and see the response (potentially copying the response to the clipboard). This when the inferior is paused after hitting a breakpoiunt, via the gdb console, which is in Codelite's Debugger > Output pane.
I was able to use the instructions at: https://sourceware.org/gdb/current/onlinedocs/gdb#Compiling-and-Injecting-Code "Compiling and injecting code in GDB" to compile simple C code and make it run in the environment of the halted inferior. For instance: compile code blah++; increments a local variable int in the inferior, which I can see via the Locals or Watch panes.
The compile file command worked fine as long as I specified the absolute path of the source file.
I was unable to see console output (to the inferior's or gdb's console) for a simple printf() statement: `printf("xxx");' because the code would not compile if there was such a line
Despite using set debug compile and set debug compile-cplus-types and checking these are set with the show versions of these, I get no error messages or acknowledgements regarding whatever I try to compile.
The blah variable is an integer, which is accessible through C code and so gcc. The ability to increment this was the only indication that my code had compiled and run.
I could not get any responses to set/show compile gcc so I am presumably compiling with gcc. I did give the command set compile gcc /usr/bin/x86_64-linux-gnu-cpp-10, but there was still no response from show compile gcc or any change in the C-only behaviour.
I could not compile the file if it contained a C++ line which incremented a data member of a class object in an vector of such objects. Nor could I compile my code if it contained C++ code such as: #include <fstream> and/or std::fstream oFile;.
The gdb documentation mentioned above is general, but does have C examples.
Is it possible to compile C++ code under gdb, injecting it into the environment of the paused inferior, with any version of gdb and gcc?
I am keen to use this C++ code injection facility, if it exists, for dumping the contents of large, complex, data structures to files and and to modify some elements of same to aid debugging.
Summary: GDB's C++ compilation and injection system does not work for me, and it is reported to be buggy or non-functional. I only tested this compile command with single lines of C code, but it worked fine for these. I was able to run my function, which writes a text dump file containing the values of a vector of class objects' data members, while the inferior was paused after a breakpoint, by including it in a source file and calling it with GDB's print or call commands, giving it the required input argument of the name of the vector to dump.
I haven't tried using GDB on its own, but at present I have no reason to believe that Codelite is interfering with my ability to communicate with GDB via Codelite's "Debugger > Output" console.
I wrote to the GDB Developer list and received what I assume is a well informed reply. I was told that in my respondent's experience "the C++ plugin isn't very functional. It seems to have some bugs and crash pretty frequently as well. Also, it seems like nobody is actively working on it." This is consistent with my experience to date.
Perhaps later versions of GDB would work better. However, there has been minimal change to the library https://github.com/gcc-mirror/gcc/commits/master/libcc1/libcp1.cc since 2017, and I could find no indication of new work on C++ compilation and injection in https://www.sourceware.org/gdb/news/ since the announcement of its introduction:
GDB 8.3.1 was released on 2019-09-20, with: "Experimental support for compilation and injection of C++ source code into the inferior (requires GCC 7.1 or higher, built with libcp1.so)."
It is possible that my problem is related to not having this library. I do have the C equivalent: /usr/lib/x86_64-linux-gnu/libcc1.so.o. I could find no such library in a Debian package. It is possible I could get this going by compiling the latest GCC/G++ and GDB, but that is pretty daunting, involving installing later standard libraries than my current Debian installation has, while making those and the newer G++ and GDB available for Codelite sessions, but not interfering with other software on machine which needs the older compilation system.
The respondent suggested that instead of compiling and injecting fresh code in the middle of a debugging session, I could write it as a library, and run it by using the compile command, on a purely C piece of code which would call it. However, for my purposes, the function needs to be passed one or more C++ constructs, and any code which called a C++ function would be C++ code and so, presumably, not be compiled by GDB.
For my immediate purpose of doing text dumps of large vectors of class objects' data members, I was able to succeed by writing such a function in an existing source file, which also contains the functions I am debugging. Then I could call it with GDB's print or call commands. I imagine this would work if the debugging function was in any other linked source file, or in a linked library. (Perhaps there is a way of writing such a library, compiling and linking it while the inferior is halted.)
I was able to run this, from a debugging session in which the inferior was halted somewhere, with either the print or call command followed by the name of the function, with the name of the vector in brackets. There must be no semicolon. I found the print command better, since GDB would report the return value, which was "void". My function used C++ constructs such as "<<" to write to the text file.
A call within my dump function of the C function system("pwd") resulted in the current directory being output on the inferior's terminal window. Likewise: print system("pwd"). print system("mc") dutifully ran Midnight Commander in the inferior's terminal window.
I altered the function to return a string, which GDB reported in the GDB "Debugger > Output" console. I added a line: std::cout << "xyz"; - but nothing appeared on either the inferior's terminal window or in the GDB console.
My attempts to use the compile command to call my dump function in exactly the same way produced no results, with or without a trailing semicolon.
I found thatprint and call work with C and C++ code while `compile" only works with C code.
I tried print vvv[6].mmm for data members which were integers, floats, and strings and GDB returned their values correctly. Adding a ++ at the end caused it to return the original integer value, but the value itself was incremented.
When I tried print with a compound line of code, with a semicolon between the two logical lines, with and without one at the end, there was no response.
The GDB Developers list is not the place for support requests, but I did not know a better way to find out about the status of this facility.
I have an OCaml program that worked fine on Ubuntu 16 but when recompiled and run on Ubuntu 20 I get the following error:-
$ ocamldebug ./linearizer
OCaml Debugger version 4.08.1
(ocd) r
Loading program... done.
Time: 89534
Program end.
Uncaught exception: Sys_error "Illegal seek"
(ocd) b
Time: 89533 - pc: 624888 - module Netaccel_link
No source file for Netaccel_link.
I thought this was due to missing dev libraries but:-
$ sudo apt install libocamlnet-ocaml-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
libocamlnet-ocaml-dev is already the newest version (4.1.6-1build6).
0 upgraded, 0 newly installed, 0 to remove and 20 not upgraded.
What setup step am I missing on Ubuntu 20?
This looks like a regression bug in libocamlnet and you should report an issue there or, I am a bit pessimistic that you will get any response, you can try to debug the issue yourself.
The problem that you are facing has nothing to do with missing libraries (they will be reported during installation or, if the package is broken, end up in linker errors). It may result, however, from some misconfiguration of the system. If that is true, then you're lucky as you can fix it yourself.
I will give you some advice that might help you in debugging this issue. For more, please try using discuss.ocaml.org as a more suitable media (SO doesn't favor this kind of a discussion and we might get deleted by admins).
The illegal seek exception is thrown when the seek operation is applied on a non-regular file, aka ESPIPE Unix error. So check your inputs. It could be that what was previously regarded as a file in Ubuntu is now a pipe or a socket.
Try to use ltrace or strace to pinpoint the culprit e.g.,
ltrace ./linearizer
or, if it overwhelms you, try strace
strace ./linearizer
Instead of using ocamldebug you can use plain gdb. You can use gdb's interfaces to provide the path to the source code (though most likely it won't work since ocamlnet is not compiled with debug information). I believe that it will give you a more meaningful backtrace.
Instead of using the system installation try using opam. Install your dependencies with opam and try older versions as well as newer versions of the OCaml compiler. Also, try different versions of ocamlnet. Ideally, try to reproduce the environment that used to work for you.
When nothing else works, you can use objdump -d and look at the disassembly of your binary. OCaml is using a pretty readable and intuitive name mangling scheme (<module_name>__<function_name>_<uid>), so you can easily find the source code (search for <module_name>.ml file and look for the <function_name> there)
Finally, just use docker or any other container to run your application. Consider switching from ocamlnet to something more modern and supported.
I have a very simple MongoDB application that connects to a MongoDB database and works fine.
I've then added the connectivity calls to a large, complex, legacy application and when I call:
mongocxx::instance (i.e. the first MongoDB library call)
I get the following response:
2018/08/16 10:20:59.0499: [16856]: ERROR: mongoc: Failed to initialize OpenSSL.
It appears that the low-level call to SSL_CTX_new within the MongoDB C library is returning a null pointer.
I'm not too sure why this is happening. I've even gone so far as recompiling and linking my simple MongoDB app against all of the libraries that the large legacy app uses (calls to ldd are now identical) but the simple app is still working fine.
This is using the following MongoDB drivers:
mongo-c-driver-1.11.0
mongo-cxx-driver-r3.3.0
Compiled and run on RHEL7 box (7.4) using OpenSSL 1.1.0.
Any suggestions?
I was just in trouble with the same error.
It solved it by changing the option of cmake.
In this way, setting an option, it will work.
cmake -DENABLE_SSL=OFF ..
In the following method, OpenSSL initialization error occurs.
cmake -DENABLE_AUTOMATIC_INIT_AND_CLEANUP = NO
I'd like to know how to prevent initialization errors with "ENABLE_AUTOMATIC_INIT_AND_CLEANUP".
https://github.com/mongodb/mongo-c-driver/blob/r1.10/NEWS#L935
https://github.com/mongodb/mongo-c-driver/blob/2edd3b2a91171a5da88e9282ffb6a3efbbc2bd91/src/libmongoc/CMakeLists.txt#L225
This problem was solved by make of OpenSSL.
Why 'apt-get install openssl' did not install last version of OpenSSL?
I used the following.
openssl-1.1.0f
mongo-c-driver-1.10.1
mongo-cxx-driver-r3.3.0
I am trying to run the autoecho program that uses boost::asio and boost::fiber. I am using the following:
Ubuntu 16
cmake 3.9.1
boost 1_65_0
That program depends on a local copy of round_robin.hpp, yield.hpp and detail/yield.hpp. I have downloaded all of those and the program builds successfully. When I run the code, I get a segmentation fault at the line in main that does:
io_svc->run();
Does anyone know if I am doing something wrong, or if the code has an error in it?
I received an email from Oliver Kowalke #boost:
unfortunately, some fixes did not permission to merged into 1.65 (no permission because too late) - you could use branch develop (github) or you need to wait till 1.66is released.
So, until boost 1.66 is released, this code will not work unless you want to use the develop branch.
I am trying to run the Woden Physics Example inside Pharo which involves getting Bullet properly compiled and the smalltalk bindings properly installed in Pharo.
I am using Linux Mint 17 x64.
But NativeBoost seems unable to load the compiled libraries. I have been using the sources provided here:
https://github.com/ronsaldo/bullet-pharo
https://github.com/ronsaldo/swig
I built the modified version of swig as well as the bullet libraries and bindings with the provided build scripts.
I also have doublechecked that the bullet libraries are 32 bit.
Opening up the Woden physics example returns this error:
failed to get a symbol address:
PharoNB_new_BTDefaultCollisionConfiguration__SWIG_1
When examining the call stack in the debugger, it turns out that the module handle is 0.
I verified this by executing the same message as
BulletCInterface nbLibraryNameOrHandle
executes:
NativeBoost forCurrentPlatform loadModule: 'BulletPharo'
This message returns 0. I tried to specify the full path to libPharoBullet.so in the workspace, like:
NativeBoost forCurrentPlatform loadModule:
'/home/martin/.local/share/Pharo/bullet-pharo/libBulletPharo.so'
with the same result. I also verified it with a 32 bit system library of mine (liblzma) and there NativeBoost was able to load it, as it returned a non-zero handle.
So i suspect something during compilation went wrong...
I also did
readelf -h libPharoBullet.so
and its ABI was "UNIX - GNU" while the ABI of pharo-vm is "UNIX - System V"
Could this be the problem here ?
How can i force the ABI to be System V when compiling ? I use gcc 4.8.2
Or what steps could i otherwise perform ?