rednaxelafx · October 31, 2013 02:24 · Oct 31, 2013
diff --git a/gdb_session b/gdb_session
@@ -0,0 +1,108 @@
+rednaxelafx@fx-laptop:/tmp
+$ gedit xx.cpp
+rednaxelafx@fx-laptop:/tmp
+$ g++ -g xx.cpp 
+rednaxelafx@fx-laptop:/tmp
+$ g++ -v
+Using built-in specs.
+Target: x86_64-linux-gnu
+Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.4.4-14ubuntu5.1' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.4 --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
+Thread model: posix
+gcc version 4.4.5 (Ubuntu/Linaro 4.4.4-14ubuntu5.1) 
+rednaxelafx@fx-laptop:/tmp
+$ gdb ./a.out 
+GNU gdb (GDB) 7.2-ubuntu
+Copyright (C) 2010 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-linux-gnu".
+For bug reporting instructions, please see:
+<http://www.gnu.org/software/gdb/bugs/>...
+Reading symbols from /tmp/a.out...done.
+(gdb) b main
+Breakpoint 1 at 0x400adf: file xx.cpp, line 6.
+(gdb) run
+Starting program: /tmp/a.out 
+
+Breakpoint 1, main () at xx.cpp:6
+6	  string foo("foo");   // (1)
+(gdb) n
+7	  string goo = foo;    // (2)
+(gdb) p foo
+$14 = {static npos = <optimized out>, 
+  _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, _M_p = 0x603028 "foo"}}
+(gdb) p/x &foo
+$15 = 0x7fffffffd750
+(gdb) x/g &foo
+0x7fffffffd750:	0x0000000000603028
+(gdb) p *(((std::string::_Rep*)foo._M_dataplus._M_p)-1)
+$16 = {<std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Rep_base> = {_M_length = 3, _M_capacity = 3, _M_refcount = 0}, 
+  static _S_max_size = <optimized out>, static _S_terminal = <optimized out>, 
+  static _S_empty_rep_storage = {0, 0, 0, 0}}
+(gdb) x/4g (((std::string::_Rep*)foo._M_dataplus._M_p)-1)
+0x603010:	0x0000000000000003	0x0000000000000003
+0x603020:	0x0000000000000000	0x00000000006f6f66
+(gdb) n
+8	  goo[0] = 'g';        // (3)
+(gdb) p foo
+$17 = {static npos = <optimized out>, 
+  _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, _M_p = 0x603028 "foo"}}
+(gdb) p/x &foo
+$18 = 0x7fffffffd750
+(gdb) x/g &foo
+0x7fffffffd750:	0x0000000000603028
+(gdb) p *(((std::string::_Rep*)foo._M_dataplus._M_p)-1)
+$19 = {<std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Rep_base> = {_M_length = 3, _M_capacity = 3, _M_refcount = 1}, 
+  static _S_max_size = <optimized out>, static _S_terminal = <optimized out>, 
+  static _S_empty_rep_storage = {0, 0, 0, 0}}
+(gdb) x/4g (((std::string::_Rep*)foo._M_dataplus._M_p)-1)
+0x603010:	0x0000000000000003	0x0000000000000003
+0x603020:	0x0000000000000001	0x00000000006f6f66
+(gdb) p goo
+$20 = {static npos = <optimized out>, 
+  _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, _M_p = 0x603028 "foo"}}
+(gdb) p/x &goo
+$21 = 0x7fffffffd740
+(gdb) x/g &goo
+0x7fffffffd740:	0x0000000000603028
+(gdb) n
+9	  cout << foo << endl;
+(gdb) p foo
+$22 = {static npos = <optimized out>, 
+  _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, _M_p = 0x603028 "foo"}}
+(gdb) p/x &foo
+$23 = 0x7fffffffd750
+(gdb) x/g &foo
+0x7fffffffd750:	0x0000000000603028
+(gdb) p *(((std::string::_Rep*)foo._M_dataplus._M_p)-1)
+$24 = {<std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Rep_base> = {_M_length = 3, _M_capacity = 3, _M_refcount = 0}, 
+  static _S_max_size = <optimized out>, static _S_terminal = <optimized out>, 
+  static _S_empty_rep_storage = {0, 0, 0, 0}}
+(gdb) x/4g (((std::string::_Rep*)foo._M_dataplus._M_p)-1)
+0x603010:	0x0000000000000003	0x0000000000000003
+0x603020:	0x0000000000000000	0x00000000006f6f66
+(gdb) p goo
+$25 = {static npos = <optimized out>, 
+  _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, _M_p = 0x603058 "goo"}}
+(gdb) p/x &goo
+$26 = 0x7fffffffd740
+(gdb) x/g &goo
+0x7fffffffd740:	0x0000000000603058
+(gdb) p *(((std::string::_Rep*)goo._M_dataplus._M_p)-1)
+$27 = {<std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Rep_base> = {_M_length = 3, _M_capacity = 3, _M_refcount = -1}, 
+  static _S_max_size = <optimized out>, static _S_terminal = <optimized out>, 
+  static _S_empty_rep_storage = {0, 0, 0, 0}}
+(gdb) x/4g (((std::string::_Rep*)goo._M_dataplus._M_p)-1)
+0x603040:	0x0000000000000003	0x0000000000000003
+0x603050:	0x00000000ffffffff	0x00000000006f6f67
+(gdb) cont
+Continuing.
+foo
+goo
+
+Program exited normally.
+(gdb) quit
+rednaxelafx@fx-laptop:/tmp
+$ 
diff --git a/xx.cpp b/xx.cpp
@@ -0,0 +1,12 @@
+#include <string>
+#include <iostream>
+using namespace std;
+
+int main() {
+  string foo("foo");   // (1)
+  string goo = foo;    // (2)
+  goo[0] = 'g';        // (3)
+  cout << foo << endl;
+  cout << goo << endl;
+  return 0;
+}