When I have stack-allocated objects in a scope (a set of commands within curly brackets), and I use next at the end of that scope, gdb jumps back to where each of the stack-allocated objects are, in reverse order.
This is disturbing during a debug ritual: When there are a lot of stack-allocated instances of objects, the debugger jumps backward to each one, and only when it is finished does it proceed forward. Instead, I expect it to proceed to the next line after the scope.
Is there a way to configure gdb to not do that, or is this some flag that I need to pass to gcc when I'm building?
At first, I thought it was that I was compiling using -O0 or something (GDB jumps to wrong lines in out of order fashion), but that is not the case here.
Here is how I am building:
/opt/rh/devtoolset-6/root/usr/bin/c++ -MD -DDEBUG -g -ggdb -gstabs+ -fPIC -Wall -Werror -Wsynth -Wno-comment -Wreturn-type main.cpp -c -o main.o
/opt/rh/devtoolset-6/root/usr/bin/c++ -MD -DDEBUG -g -ggdb -gstabs+ -fPIC -Wall -Werror -Wsynth -Wno-comment -Wreturn-type main.o -L. -L/opt/rh/devtoolset-6/root/usr/lib64 -lstdc++ -o main.exe
Below is what I'm seeing in the debugger. Notice the version of GDB involved:
bash-4.2$ gdb main.exe
GNU gdb (GDB) Red Hat Enterprise Linux 7.12.1-48.el6
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from main.exe...done.
(gdb) b main
Breakpoint 1 at 0x400a27: file main.cpp, line 45.
(gdb) r
Starting program: /home/brentg/scratch_sandboxes/cxxminimal/main.exe
Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.192.el6.x86_64
Breakpoint 1, main (argc=1, argv=0x7fffffffeb38, envp=0x7fffffffeb48)
at main.cpp:45
45 std::cout << __FILE__ << ":" << __LINE__ << ":" << "main begin" << std::endl;
Missing separate debuginfos, use: debuginfo-install libgcc-4.4.7-17.el6.x86_64 libstdc++-4.4.7-17.el6.x86_64
(gdb) l
40 std::cout << __FILE__ << ":" << __LINE__ << ":" << "printing some info 2" << std::endl;
41 }
42
43 int main(int argc, char *argv[], char *const envp[])
44 {
45 std::cout << __FILE__ << ":" << __LINE__ << ":" << "main begin" << std::endl;
46 some_function_that_uses_Foo();
47 std::cout << __FILE__ << ":" << __LINE__ << ":" << "main end" << std::endl;
48 return 0;
49 } // end main
(gdb) n
main.cpp:45:main begin
46 some_function_that_uses_Foo();
(gdb) s
some_function_that_uses_Foo () at main.cpp:38
38 std::cout << __FILE__ << ":" << __LINE__ << ":" << "printing some info 1" << std::endl;
(gdb) n
main.cpp:38:printing some info 1
39 Foo the_foo1;
(gdb) n
40 std::cout << __FILE__ << ":" << __LINE__ << ":" << "printing some info 2" << std::endl;
(gdb) l
35
36 void some_function_that_uses_Foo()
37 {
38 std::cout << __FILE__ << ":" << __LINE__ << ":" << "printing some info 1" << std::endl;
39 Foo the_foo1;
40 std::cout << __FILE__ << ":" << __LINE__ << ":" << "printing some info 2" << std::endl;
41 }
42
43 int main(int argc, char *argv[], char *const envp[])
44 {
(gdb) n
main.cpp:40:printing some info 2
39 Foo the_foo1;
At this point, I wonder: Why am I now back on line 39? When I was on line 40, entering in "next", then it seemingly jumps backwards.
Looking at the gdb manual for the "next" command, I do not see anything in regards to C++ constructors/destructors.
