If the last lines printed were printed with a each repetition moves up in the source file. Type/Address This format allows explicitly specifying the address of the evaluated expression and can be used as a shortcut to the C/C++ type conversion. You are currently viewing LQ as a guest. execution in that frame has stopped. used to build it. Setting count to unlimited or 0 means there’s no limit. Print lines centered around the beginning of function You can print other portions of the current working directory, unless it happens to be in the source the executable search path is not used for this purpose. to specify some source line. Display the number of lines that list prints. I have tried the 'list' command and it shows the lines around the current line. In this example, GDB pauses the program just before executing line 36 of the program. Also, info line prints addresses in symbolic form as It opens the gdb console of the current program, after printing the version information. An exception is made for an list linenum. Is there a better way to print the current line number? Print lines from first to last. this is called the source path. 9.1 Printing Source Lines. Hi, How can I print the current source line number in gdb? gdb is capable to print out arguments passed to functions. ... Print all directories in which GDB sear-ches for source files. On the other hand, gcc 4.4 + newer ld doesn't exhibit the problem. Naming . than listing the same lines again. You can drag and drop the views in Qt Creator to new … Syntax: print {variable} Examples: print i print j print num (gdb) p i $1 = 1 (gdb) p j $2 = 3042592 (gdb) p num $3 = 3 (gdb) As you see above, in the factorial.c, we have not initialized the variable j. Alternately, you can set GDB to print the source file and line number when it prints a symbolic address: set print symbol-filename on Tell GDB to print the source file name and line number of a symbol in the symbolic form of an address. versions of source. list
: list , Shows the current or given source con-text. (see section Selecting a frame), GDB prints the line where Hi, How can I print the current source line number in gdb? locations. Also: function name, address, filename:function or filename:line-number. If last is omitted the context starting at start is printed instead of centered a-round it. List a specific file and line number: (gdb) l regexp.go:1 (gdb) # Hit enter to repeat last command. However, NASM doesn't generate the line number information for gdb, so you must set the breakpoints according to addresses relative to labels in the assembly language program. If the source path is empty, and there is no record of the set print symbol-filename off Do not print source file name and line number of a symbol. End with a line saying just "end". list line-number list function list - list start#,end# list filename:function: List source code. linespec) what source line covers a particular address: After info line, the default address for the x command You can change this using set listsize: set listsize count Make the list command display count source lines (unless the list argument explicitly specifies some other number… Upon reaching a breakpoint, GDB pauses the program before executing the line of code at the breakpoint, and prints out the breakpoint number and source code line associated with the breakpoint. Every time you create a breakpoint, it's assigned a number. source file of the second location is omitted, this refers to However, NASM doesn't generate the line number information for gdb, so you must set the breakpoints according to addresses relative to labels in the assembly language program. object program records a directory, GDB tries that directory So far as I understand, that universally indicates the source code is out of sync with the debug info (in Linux the debug info typically stays together with the binary, so that means this binary wasn't built from that source). It will display list of currently set breakpoints with other useful information. Additionally if you want to check list of currently set breakpoints, you can use info break command. This is the default. compilation directory, GDB looks in the current directory as a Alternatively, a line number can be used to add a breakpoint as well. You can see these breakpoints with the GDB maintenance command `maint info breakpoints'. Repeating a list command with RET discards the argument, Set a breakpoint on function. Methods must be qualified with the name of their receiver types. m4_changequote: We can also inquire (using *addr as the form for well as hex. quit or q –> exits out of gdb. as part of displaying a stack frame (see Examining the In general, the list command expects you to supply zero, one or two locations. help – View help for a particular gdb topic — help TOPICNAME. This is more useful You can change this using set listsize: set listsize count Make the list command display count source lines (unless the list argument explicitly specifies some other number). There are two commands for searching through the current source file for a list command, this prints lines following the last lines each line is in the file. line specified. until line-number: Continue processing until you reach a specified line number. By default, GDB prints ten source lines with any of these forms of the list command. This explains why I was able to reproduce the lack of line numbers in gdb on nsBlockFrame::Reflow with gcc 4.4 + ld from fedora 12, but not with gcc 4.5 + same ld. These internal breakpoints are assigned negative numbers, starting with -1; `info breakpoints' does not display them. information recorded in the program tells GDB what source files were So it stopped execution when it reached line number 17. l command: Use gdb command l or list to print the source code in the debug mode. You can do this the same way you would on the unix command line, except that you are saying run instead of the program name. mode, the info line command now causes the arrow to point to the If you want to delete a breakpoint, just use the delete command. Even when they do, By default, ten lines are printed. Probably it’s already too much to ask for PS 2. shows SPARC machine instructions): Go to the first, previous, next, last section, table of contents. To print lines from a source file, use the list command It tells GDB to output the full file name and line number in a standard, recognizable fashion each time a stack frame is displayed (which includes each time the program stops). Print more lines. Here is a complete description of the possible arguments for list: Here are the ways of specifying a single source line--all the Print lines just after the lines last printed. kinds of linespec. Here are the forms of the list command most commonly used: . Variable and function names must be qualified with the name of the packages they belong to. If your source path is cluttered with directories that are no longer of files from which they were compiled, just the names. the directories could be moved between the compilation and your debugging By default, GDB prints ten source lines with any of these forms of the list command. Step through Breakpoints . set print symbol-filename off Do not print source file name and line number of a symbol. GDB can print parts of your program's source, since the debugging You should take a look at the source code available on method #4, which also prints line numbers and filenames. In the below image, the program was executed twice, one with the command line argument 10 and another with the command line argument 1, and their corresponding outputs were printed. Print lines just before the lines last printed. The availability of views depends on whether you are debugging C++ or QML. An exception is made for an The Compile function from the regexp package is known to GDB as 'regexp.Compile'. Print lines just before the lines last printed. To print lines from a source file, use the list command (abbreviated l).By default, ten lines are printed. set print symbol-filename off Do not print source file name and line number of a symbol. In general, the list command expects you to supply zero, one or two For example: (gdb) up #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc) at env.c:10 10 read_input_file (argv[i]); After such a printout, the list command with no arguments prints ten lines centered on the point of execution in the frame. the list command. 6. Each time GDB wants a source file, Executable programs sometimes do not record the directories of the source The filename may be omitted. We can also inquire (using *addr as the form for linespec) what source line covers a particular address: (gdb) info line *0x63ff Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404. Mistakes, optimizations, etc. And for Arch Linux, you need to run: sudo pacman -S gdb. So, it gets garbage value resulting in a big numbers as factorial values. Alternately, you can set GDB to print the source file and line number when it prints a symbolic address: set print symbol-filename on. Stack), this prints lines centered around that line. Print lines just before the lines last printed. When a list command has two locations, and the Alternately, you can set GDB to print the source file and line number when it prints a symbolic address: set print symbol-filename on Tell GDB to print the source file name and line number of a symbol in the symbolic form of an address. There are several ways to specify what part of the file you want to print; see Specify Location, for the full list.. line_number Break/watch the line number in the cur-rent source file. Use the command continue to continue the execution of the program. the object code for the first line of function GDB itself sometimes sets breakpoints in your program for special purposes, such as proper handling of longjmp (in C programs). so it is equivalent to typing just list. Alternately, you can set gdb to print the source file and line number when it prints a symbolic address: set print symbol-filename on Tell gdb to print the source file name and line number of a symbol in the symbolic form of an address. any information it has cached about where source files are found and where show print symbol-filename. is changed to the starting address of the line, so that `x/i' is linespecs. For example: break *_start+5 The breakpoint can be set either with the address of the instruction(in hexadecimal form … This is the default. the list argument explicitly specifies some other number). When using gdb with C/C++ programs, you can set breakpoints by the line number of the statement in the source file. (abbreviated l). Once the command is successful, it prints the breakpoint number, information of the program counter, file name, and the line number. bt: backtrack – Print backtrace of all stack frames, or innermost COUNT frames. This is the default. There are several ways to specify what part of the file you want to print. 2. When printing variables - gdb prints them on a single long line. For example, we can use info line to discover the location of whatis variable_name than listing the same lines again. To change the default settings, select Window > Views, and then select views to display or hide. This is the default. to use Similar question (thanks nobar) Answers: Not too long ago I answered a similar question. Whenever you reset or rearrange the source path, GDB clears out directory directory-name dir directory-name show directories: Add specified directory to front of source code path. of writing them but the effect is always to specify some source line. (gdb) break printf. the same source file as the first location. l command: Use gdb command l or list to print the source code in the debug mode. For example: (gdb) up #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc) at env.c:10 10 read_input_file (argv[i]); The second line shows the text of that source line. show listsize Display the number of lines that list prints. the source file. The first line shows the frame number, the function name, the arguments, and the source file and line number of execution in that frame. Do not print source file name and line number of a symbol. ... (gdb) quit Notice the native GDB print "p" results in an cryptic display while the "pvector" routine from the GDB script provided a … In Debug mode, you can use several views to interact with the program you are debugging. This one is simple, but a huge timesaver if you didn't know it. a range of addresses as machine instructions. bt: backtrack – Print backtrace of all stack frames, or innermost COUNT frames. Signals handle Set how to handle signles. In order to get the most useful information during debugging, such as variable names and line numbers, the program should be compiled in a special way. Also, this address is saved as the value of the source files by explicit command. Neither is When your program stops, GDB spontaneously prints Inside GDB, your program may stop for any of several reasons, such as a signal, a breakpoint, or reaching a new line after a GDB command such as step. (gdb) info line m4_changecom Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350. printed; however, if the last line printed was a solitary line printed Frequently, the source line understood by gdb for an ip value is not just the wrong line, but a blank line. To add other directories, use the directory command. run [args] : This command runs the current executable file. So, it gets garbage value resulting in a big numbers as factorial values. GDB Tutorial Gdb is a debugger for C (and C++). You can give command line arguments to your program on the gdb command line. >print addr >print len >print prot >end (gdb) gdb --args. occurred in your program. By default, ten lines are printed. As it encounters any breakpoint during execution, it prints the breakpoint number, function name with the values of the arguments, file name, and line number. Now the gdb debugger is installed and you can use it. This is more useful set print symbol-filename off Do not print source file name and line number of a symbol. When you start GDB, its source path is empty. Fix this issue by initializing variable j with 1, compile the C program and execute it again. function. By default, GDB prints ten source lines with any of these forms of (gdb) continue. clear –> to clear all breakpoints. (gdb) b do_mmap_pgoff Breakpoint 1 at 0xffffffff8111a441: file mm/mmap.c, line 940. so it is equivalent to typing just list. help – View help for a particular gdb topic — help TOPICNAME. Enter the run command and the program will stop at the breakpoint. in the list, until it finds a file with the desired name. file:line_number Break/watch the line number in the named source file. print; see Specify Location, for the full list. This is the default. too. set print symbol-filename off. However, this command has "memory" and doesn't show the same lines each time it is executed. There are several ways to specify what part of the file you want to print expr Display the value of an expression. continue –> continue normal execution. This is the default. Step 5. (gdb) command 1 Type commands for when breakpoint 1 is hit, one per line. Here are the forms of the list command most commonly used: By default, GDB prints ten source lines with any of these forms of set listsize Set how many lines to show in „list“. Likewise, when you select a stack frame 5.Now, type “l” at gdb prompt to display the code. Alternately, you can set GDB to print the source file and line number when it prints a symbolic address: set print symbol-filename on Tell GDB to print the source file name and line number of a symbol in the symbolic form of an address. Frequently used views are shown by default and rarely used ones are hidden. path. When run under GNU Emacs it tries all the directories in the list, in the order they are present By default, GDB prints ten source lines with any of these forms of the list command. We can use disassemble to inspect the object code of writing them (see Specify Location), but the effect is always However, this command has "memory" and doesn't show the same lines each time it is executed. Is there a better way to print the current line number? For example: break *_start+5 Stops the execution of the program 5 bytes after the address labeled by _start. Compiling the program. set print symbol-filename off Do not print source file name and line number of a symbol. the list command. E.g. Note that sufficient to begin examining the machine code (see section Examining memory). Notices: Welcome to LinuxQuestions.org, a friendly and active Linux Community. Locations specify source lines; there are several ways You can change this using set listsize: set listsize count Make the list command display count source lines (unless the list argument explicitly specifies some other number). argument of `-'; that argument is preserved in repetition so that show listsize Display the number of lines that list prints. Alternately, you can set GDB to print the source file and line number when it prints a symbolic address: set print symbol-filename on Tell GDB to print the source file name and line number of a symbol in the symbolic form of an address. GDB has a list of directories to search for source files; Alternatively, you can enable or disable views from the context menu of the title bar of any visible debugger view. Emacs facilities to view source; see section Using GDB under GNU Emacs. When this format is used and i is specified as the previous value number, the print command will repeat the output produced by its i-th invocation. Simplest way of putting a breakpoint is using the function name or a line number. Here, this lists next 10 lines. (gdb) break 6. Use l line-number to view a specific line number (or) l function to view a specific function. Both arguments are This recognizable format looks like two \032 characters, followed by the file name, line number and character position separated by colons, and a newline. Linespecs specify source lines; there are several ways last resort. For example, run 5 20 40 60. You can change this using set listsize: Repeating a list command with RET discards the argument, To print lines from a source file, use the list command See section Printing source lines. sudo dnf install gdb. GDB can not find line numbers User Name: Remember Me? Here is a complete description of the possible arguments for list: Print lines centered around the line specified by location. (abbreviated l). interest, GDB may sometimes cause confusion by finding the wrong each repetition moves up in the source file. Let’s introduce a break point, say line 5. the line where it stopped. You can even do input/output redirection: run > outfile.txt. Print lines just before the lines last printed. You can change this using set listsize: Make the list command display count source lines (unless Next: Specify Location, Up: Source [Contents][Index]. show listsize Print how many are shown in the „list“ command. regular expression. Use l line-number to view a specific line number (or) l function to view a specific function. session. Here are the forms of the list command most commonly used: Print lines centered around line number linenum in the Tell GDB to print the source file name and line number of a symbol in the symbolic form of an address. directory: Clear sourcepath when nothing specified. You can correct the situation as follows: You can use the command info line to map source lines to program If GDB cannot find a source file in the source path, and the The second line shows the text of that source line. set listsize count show listsize : Number of lines listed when list command given. If you use GDB through its GNU Emacs interface, you may prefer In this example, breakpoint is set on line number 17 of breakpoint_example.c file. Printing the variable values inside gdb debugger Syntax: print {variable} Examples: print i print j print num (gdb) p i $1 = 1 (gdb) p j $2 = 3042592 (gdb) p num $3 = 3 (gdb) As you see above, in the factorial.c, we have not initialized the variable j. convenience variable $_ (see section Convenience variables). It allows you to do things like run the program up to a certain point then stop and print out the values of certain variables at that point, or step through the program one line at a time and print out the values of each variable after executing each line. Password: Linux - Kernel This forum is for all discussion relating to the Linux kernel. addresses (and vice versa), and the command disassemble to display You may then examine and change variables, set new breakpoints or remove old ones, and then continue execution. range shown in the last info line example (the example To set a breakpoint at a particular line number in myprogram.c: (gdb) b myprogram.c:47 Breakpoint 2 at 0x400a8c: file myprogram.c, line 47. I have tried the 'list' command and it shows the lines around the current line. print or p –> used to display the stored value. current source file. argument of ‘-’; that argument is preserved in repetition so that