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debugginggdbshared-librariesmex
Pouya
Pouya

Reputation: 1959

Could not Load Shared Library Symbols, GDB

I am calling a shared library (QSP.so) from MATLAB. The library is written in C and using a mex gateway, the data are passed the shared library. It seems that there is some bug in my C code as I have following problems:

1) In MATLAB, when I call the gateway function, MATLAB freezes most of the time. 2) When I use GDB to debug the code, as described Here, and set a breakpoint at the entry function (QSP), GDB does not stop at the breakpoint and creates following error:

warning: Could not load shared library symbols for ./QSP.so.
Do you need "set solib-search-path" or "set sysroot"?

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb289db40 (LWP 4234)]
0xb72a7a0e in ?? () from /lib/i386-linux-gnu/libc.so.6

I am pretty sure there is nothing wrong with the gateway as when I do not call the shared library, everything is fine. Without any debugger, on the other hand, it would be too hard to find the problem. So, I would like to know how I can get GDB stop at the breakpoint.

Also, following is my Makefile:

CC = gcc
CFLAGS = -c -fpic -Wall -Werror -O3 -g

all: QSP.o ExtraRoutines.o
    $(CC) -shared -o QSP.so -g $^

QSP.o: QSP.c ExtraRoutines.c QSP.h 
    $(CC) $(CFLAGS) $^

ExtraRoutines.o: ExtraRoutines.c QSP.h
    $(CC) $(CFLAGS) $^

Moving:
    mv -f QSP.so ../

Clean:
    rm *.o

As can be seen, I use -g flag for both .o and .so files

Any help is appreciated and thanks in advance.

Upvotes: 1

Views: 21249

Answers (3)

Alijoonami
Alijoonami

Reputation: 61

In case anybody else has this question, the answer is the same as given in this question.

You need a .gdbinit file that points to your shared library. I'm using Eclipse and I simply give the .gdbinit I made with that one line to "attach to Process" configuration for debugging the c++ program. Assuming the .gdbinit file is in the root of the eclipse project which has a Debug folder where the shared library is, the line would be

set solib-search-path ./Debug/

Upvotes: 3

Zlopez
Zlopez

Reputation: 700

As I can see, you are using relative path for QSP.so.

Try changing the directory to path where the QSP.so is.

For example QSP.so is in /home/user/project/QSP.so:

  1. cd /home/user/project/
  2. gdb <app>

Upvotes: 0

Brian Tiffin
Brian Tiffin

Reputation: 4116

I think the answer is in the error message,

Do you need "set solib-search-path" or "set sysroot"?

Maybe stash an appropriate setting in your home .gdbinit to see if you can help gdb find the symbol table.

Upvotes: 3

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