I am debugging C code with gdb and I get an error I don't understand.
My code has this line:
101 tmp[0] = path[0];
after executing the line I want to print tmp (which is char*) I get this message:
(gdb) out tmp
No symbol "tmp" in current context.
Can anyone help?
Thanks,
Dudy.
It most likely was optimized away, or else compiled without debug symbols.
Try compiling with -O0 to remove optimizations and with -g to have debug symbols.
Related
When I build clang I add the flag -DCMAKE_BUILD_TYPE=Debug.
Now I want to debug my clang.
I do gdb build/bin/clang. But when I want to add a breakpoint break llvm/lib/Transforms/Instrumentation/AddressSanitizer:instrumentStoreInstruction and gdb throw an error
Function "instrumentStoreInstruction" not defined in "/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp".
But prototype and definition of that function are in that file.
I've used CodeRunner (http://krillapps.com/coderunner) for a long time but recently I can't compile any C or C++ code in it. This started happening around the time I updated to Xcode 5.1. I can still compile and run as normal in Xcode.
When I try to run in CodeRunner, the following error is printed.
clang: error: unknown argument: '-finput-charset=UTF-8' [-Wunused-command-line-argument-hard-error-in-future]
clang: note: this will be a hard error (cannot be downgraded to a warning) in the future
There is already a solution for Objective C:
Clang error when compiling in CodeRunner
Does anyone know how to modify the script for C++/ C?
Thanks in advance.
There is a similar bug with the object-c compilation, the link to fix that is
Clang error when compiling in CodeRunner,
and you just need do as below for the c/c++ situation:
g++ "$1" -o "$compname" -finput-charset=${enc[$2]} $3
g++ "$1" -o "$compname" $3
I am trying to debug a C++ program in Eclipse using gdb. I think it works fine in my main() function, but elsewhere it gives me a warning when I try to look at the value of a variable:
Failed to execute MI command:
-data-evaluate-expression variable
Error message from debugger back end:
Could not find the frame base for "Class::method()".`
After scouring the internet, I am having a hard time understanding what this error means or finding out how to fix the problem. There are a few other similar questions (here and here) floating around Stack Overflow.
Since Apple's Xcode command line tools are painfully out-of-date (see gcc and gdb issues) I needed to use my own homebrewed versions. I don't know if there is something in the setup for these tools that I might have missed.
I can debug from command line using gdb and I hit the same error: "Could not find the frame base for "Class::method()", so I'm pretty sure it is not an issue with Eclipse.
Does anything jump out to anyone, that might be causing this problem?
Mac OS X 10.8.5 (Mountain Lion)
Eclipse 4.2.1 (Juno)
gcc 4.8.2 (homebrewed) (with -O0 and -g3)
gdb 7.6.2 (homebrewed and codesigned)
Update:
I am also seeing the line:
BFD: /System/Library/Frameworks/CFNetwork.framework/Versions/A/CFNetwork(i386:x86-64): unknown load command 0x20
Followed by several warnings:
warning: Could not open OSO archive file "/private/tmp/gcc48-KqoQ/gcc-4.8.2/build/x86_64-apple-darwin12.5.0/libstdc++-v3/src/../libsupc++/.libs/libsupc++convenience.a"
warning: Could not open OSO archive file "/private/tmp/gcc48-KqoQ/gcc-4.8.2/build/x86_64-apple-darwin12.5.0/libstdc++-v3/src/../src/c++11/.libs/libc++11convenience.a"
warning: Could not open OSO archive file "/private/tmp/gcc48-KqoQ/gcc-4.8.2/build/x86_64-apple-darwin12.5.0/libstdc++-v3/src/../src/c++98/.libs/libc++98convenience.a"
warning: `/private/tmp/gcc48-KqoQ/gcc-4.8.2/build/x86_64-apple-darwin12.5.0/libstdc++-v3/src/.libs/compatibility-atomic-c++0x.o': can't open to read symbols: No such file or directory.
warning: `/private/tmp/gcc48-KqoQ/gcc-4.8.2/build/x86_64-apple-darwin12.5.0/libstdc++-v3/src/.libs/compatibility-c++0x.o': can't open to read symbols: No such file or directory.
warning: `/private/tmp/gcc48-KqoQ/gcc-4.8.2/build/x86_64-apple-darwin12.5.0/libstdc++-v3/src/.libs/compatibility-chrono.o': can't open to read symbols: No such file or directory.
warning: `/private/tmp/gcc48-KqoQ/gcc-4.8.2/build/x86_64-apple-darwin12.5.0/libstdc++-v3/src/.libs/compatibility-debug_list-2.o': can't open to read symbols: No such file or directory.
...
which continues for several lines. Google searches for "gdb bfd unknown load command" reveal a lot of sites without any solution, but they all seem to indicate that there may be a conflict between non-apple versions of gdb and Mac OS X 10.8+.
Any insight would help a ton!
It's because the name mangling. Names are mangled same with GCC and Clang (they often share similar mechanisms). Name mangling makes it available to have C/C++ method and Assembly procedure with the same name. See what happens to a C definition:
void myfunc() {}
We use nm to view binary names of symbols. Use nm --demangle to view unmangled names. Nm output for compiled file is:
...
0000000000000000 T _myfunc
...
Number of other symbols depends on debugging level, see GCC manpage for -O and -g options. As we see, there is a number. It's hexadecimal. It has eight digits on 32bit machines and sixteen digits on 64bit machines (it's because n-bit CPU means that n-bits represent a pointer, the symbol is really a pointer inside the binary file). Then we have symbol type. Only two values are interesting now: T is a C/C++/... method, t is an assembler procedure. See what goes on if we compile following assembly code:
myproc:
GCC and Clang shouldn't push debugging symbols when compiling Assembly, so nm output will probably look like:
0000000000000000 t myproc
Assembly procedure names are not mangled. C++ is mangled, very strangely. Some characters, like : or , are not allowed in symbol name. Compile this C++ source:
namespace myspace { void myfunc() {} }
We see output:
...
0000000000000000 T __ZN7myspace6myfuncEv
...
And main method name is never mangled. If we have like this:
int main(int argc, char** argv) {}
int main(std::vector<std::string> args) {}
only the second name is mangled. I think this may be the problem. And, these warnings mean NOTHING. They mean that system was recompiled with low debugging symbol count.
I am compiling a project under VS2012 and GCC (CodeBlocks) for Windows.
On VS2012 everything works perfect. Under GCC I am obtaining the following compiling error:
C:\Users\Piotrek\AppData\Local\Temp\ccfdl0Ye.s|164|Error: invalid use of register|
C:\Users\Piotrek\AppData\Local\Temp\ccfdl0Ye.s|166|Error: invalid use of register|
C:\Users\Piotrek\AppData\Local\Temp\ccfdl0Ye.s|221|Error: invalid use of register|
||=== Build finished: 3 errors, 14 warnings (0 minutes, 0 seconds) ===|
I am using the compiler option -fpermissive - It should have nothing to do with the error.
I just can't understand why is it pointing to a temporary file under the Local Temp folder, and saying that I am using a wrong register??
Does anybody have any idea on what's happening?
It looks like you've encountered a bug in the compiler. The
error messages (judging from the "source" file name) are from
the assembler. The only time the assembler should generate an
error message is when there is something illegal in the
assembler, and the C++ compiler should never generate illegal
assembler; if it can't generate legal assembler, it should
output an error message and fail.
The real problem, when you get this sort of message, is to
figure out what in your code is triggering it. g++ has an
option which tells it to not delete any of the intermediate
files. Use this, then try and see what is going on in the
assember files at these lines. (When you ask g++ to output
assembler, it puts nice comments in to help finding the
corresponding source. I don't know if it also does this when
generating assembler as an intermediate file.) And then try
cutting code (if worse comes to worse, using binary search)
until you can get the error for a program of one or two lines.
Try to guess what's special about them, and change them to do
the same thing, in a different way.
And don't fail to report the error to g++.
Thanks to James Kanze's recommendation, I decided to tell to the compiler not to delete temporary files. This is done by the flag:
-save-temps
As James said, the assembler generates some nice comments which inform exactly which line on our C++ code is throwing the error. In my case, it looks like it is not accepting such instruction:
asm
(
".intel_syntax noprefix\n"
"lock dec [DWORD PTR eax]\n"
".att_syntax \n"
:
: "a" (data)
:
);
I don't know why he is not accepting Intel Syntax anymore, since it was working with previous GCC version, and now that I updated it it doesn't anymore.
Anyway, the solution for such problems is the one mentioned by James: Just dont delete intermediate files so that you can spy directly into Assembly code what's wrong.
About the problem of the INTEL syntax, any idea why it doesn't work anymore?
I am trying to compile a c++ program in Linux, using the command in the shell
$ g++ -Wall *.cpp -o prog
and for some reason it keeps on giving me a weird error:
g++: Internal error: Bus error (program cc1plus) Please submit a full
bug report. See for
instructions.
I searched the net for this bus error, and it says that it has to do with something about accessing illegal memory.
Can someone maybe clarify things a bit more for me?
This error message is telling you that there's a bug in the g++ compiler itself.
Try to narrow it down by removing bits and pieces of your source file until the problem goes away. You're not trying to fix your program, you're just trying to find the part that is breaking the compiler. Once you've found it, you can either give a better bug description or you can change your code to work around it.
Or just download the latest version of the g++ compiler and hope that it's already fixed.
Your problem is not in your code, is the compiler (g++) that is crashing and producing that Bus Error, it's possible you have an outdated version of such compiler and need to update, or you're lucky and found a real bug in g++.
I would try compiling each source file separately, to check what part of the source code triggers the error.