This is a regression (see also bug #149603):
- create two Welcome samples
- set Line BP in one of them in welcome .cc in line 38, make sure that the BP is not displayed in the second project
- start debugging the second project
Result: The BP appears in source code of the second project and debugger stops at the BP.

Here is debugger log:
~"GNU gdb 6.8-debian\n"
~"Copyright (C) 2008 Free Software Foundation, Inc.\n"
~"License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>\n"
~"This is free software: you are free to change and redistribute it.\n"
~"There is NO WARRANTY, to the extent permitted by law.  Type \"show copying\"\n"
~"and \"show warranty\" for details.\n"
~"This GDB was configured as \"i486-linux-gnu\".\n"
&"/home/ap153252/.gdbinit: No such file or directory.\n"
(gdb) 
1-gdb-set print repeat 0
2-gdb-set backtrace limit 1024
3-file-exec-and-symbols  "/home/ap153252/NetBeansProjects/Welcome_19/dist/Debug/GNU-Linux-x86/welcome_19"
1^done
(gdb) 
2^done
(gdb) 
3^done
(gdb) 
4-file-list-exec-source-file
5cd /home/ap153252/NetBeansProjects/Welcome_19
6-exec-arguments "arg 1" "arg 2" "arg 3" "arg 4"
4^done,line="26",file="welcome.cc",fullname="/home/ap153252/NetBeansProjects/Welcome_19/welcome.cc",macro-info="0"
(gdb) 
7-break-insert welcome.cc:38
1
8-break-insert -t _start
&"cd /home/ap153252/NetBeansProjects/Welcome_19\n"
~"Working directory /home/ap153252/NetBeansProjects/Welcome_19.\n"
5^done
(gdb) 
6^done
(gdb) 
7^done,bkpt={number="1",type="breakpoint",disp="keep",enabled="y",addr="0x08048789",func="main",file="welcome.cc",fullname="/home/ap153252/NetBeansProjects/Welcome_19/welcome.cc",line="38",times="0"}
(gdb) 
&"\n"
1^done
(gdb) 
8^done,bkpt={number="2",type="breakpoint",disp="del",enabled="y",addr="0x08048640",file="../sysdeps/i386/elf/start.S",line="65",times="0"}
(gdb) 
No command for record 1^done
9-exec-run
9^running
(gdb) 
~"Current language:  auto; currently asm\n"
9*stopped,thread-id="0",frame={addr="0x08048640",func="_start",args=[],file="../sysdeps/i386/elf/start.S",line="65"}
(gdb) 
10info proc
&"info proc\n"
~"process 5027\n"
~"cmdline = '/home/ap153252/NetBeansProjects/Welcome_19/dist/Debug/GNU-Linux-x86/welcome_19'\n"
~"cwd = '/home/ap153252/NetBeansProjects/Welcome_19'\n"
~"exe = '/home/ap153252/NetBeansProjects/Welcome_19/dist/Debug/GNU-Linux-x86/welcome_19'\n"
10^done
(gdb) 
11-exec-continue
11^running
(gdb) 
~"Current language:  auto; currently c++\n"
11*stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",frame={addr="0x08048789",func="main",args=[{name="argc",value="5"},{name="argv",value="0xbfc6e244"}],file="welcome.cc",fullname="/home/ap153252/NetBeansProjects/Welcome_19/welcome.cc",line="38"}
(gdb) 
12-stack-list-frames
12^done,stack=[frame={level="0",addr="0x08048789",func="main",file="welcome.cc",fullname="/home/ap153252/NetBeansProjects/Welcome_19/welcome.cc",line="38"}]
(gdb) 
13-stack-list-arguments 1
13^done,stack-args=[frame={level="0",args=[{name="argc",value="5"},{name="argv",value="0xbfc6e244"}]}]
(gdb)