[PATCH v4 9/9] Explicit locations: documentation updates

Keith Seitz
2015-05-07T18:13:16Z

This patch adds documentation for explicit locations to both the
User Manual and gdb's online help system.

gdb/ChangeLog:

* NEWS: Mention explicit locations.
* breakpoint.c [LOCATION_HELP_STRING]: New macro.
[BREAK_ARGS_HELP]: Use LOCATION_HELP_STRING.
(_initialize_breakpoint): Update documentation for
"clear", "break", "trace", "strace", "ftrace", and "dprintf".

gdb/doc/ChangeLog:

* gdb.texinfo (Thread-Specific Breakpoints): Use "location(s)"
instead of "linespec(s)".
(Printing Source Lines): Likewise.
(Specifying a Location): Rewrite. Add explanations for each
location type.
(Source and Machine Code): Use "location(s)" instead of
"linespec(s)".
(C Preprocessor Macros): Likewise.
(Create and Delete Tracepoints): Likewise.
(Extensions for Ada Tasks): Likewise.
(Continuing at a Different Address): Remove "linespec" examples.
Add reference to "Specify a Location"
(The -break-insert Command): Rewrite. Add anchor.
Add reference to appropriate manual section discussing locations.
(The -dprintf-insert Command): Refer to -break-insert for
specification of 'location'.

gdb/testsuite/ChangeLog:

* gdb.base/help.exp: Update help_breakpoint_text.
---
gdb/NEWS | 4 +
gdb/breakpoint.c | 70 +++++++-----
gdb/doc/gdb.texinfo | 234 +++++++++++++++++++++++++--------------
gdb/testsuite/gdb.base/help.exp | 2
4 files changed, 195 insertions(+), 115 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index 0c7084a..9eaa69b 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -270,6 +270,10 @@ VAX running Ultrix vax-*-ultrix*
-D data-directory
This is an alias for the --data-directory option.

+* GDB now allows users to specify explicit locations, bypassing
+ the linespec parser. This feature is also available to GDB/MI
+ clients.
+
* GDB supports printing and modifying of variable length automatic arrays
as specified in ISO C99.

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 58c3cd7..e4bcab4 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -15574,26 +15574,46 @@ all_tracepoints (void)
}

\f
+/* This help string is used to consolidate all the help string for specifying
+ locations used by several commands. */
+
+#define LOCATION_HELP_STRING \
+"Linespecs are colon-separated lists of location parameters, such as\n\
+source filename, function name, label name, and line number.\n\
+Example: To specify the start of a label named \"the_top\" in the\n\
+function \"fact\" in the file \"factorial.c\", use\n\
+\"factorial.c:fact:the_top\".\n\
+\n\
+Address locations begin with \"*\" and specify an exact address in the\n\
+program. Example: To specify the fourth byte past the start function\n\
+\"main\", use \"*main + 4\".\n\
+\n\
+Explicit locations are similar to linespecs but use an option/argument\n\
+syntax to specify location parameters.\n\
+Example: To specify the start of the label named \"the_top\" in the\n\
+function \"fact\" in the file \"factorial.c\", use \"-source factorial.c\n\
+-function fact -label the_top\".\n"
+
/* This help string is used for the break, hbreak, tbreak and thbreak
commands. It is defined as a macro to prevent duplication.
COMMAND should be a string constant containing the name of the
command. */
+
#define BREAK_ARGS_HELP(command) \
command" [PROBE_MODIFIER] [LOCATION] [thread THREADNUM] [if CONDITION]\n\
PROBE_MODIFIER shall be present if the command is to be placed in a\n\
probe point. Accepted values are `-probe' (for a generic, automatically\n\
guessed probe type), `-probe-stap' (for a SystemTap probe) or \n\
`-probe-dtrace' (for a DTrace probe).\n\
-LOCATION may be a line number, function name, or \"*\" and an address.\n\
-If a line number is specified, break at start of code for that line.\n\
-If a function is specified, break at start of code for that function.\n\
-If an address is specified, break at that exact address.\n\
+LOCATION may be a linespec, address, or explicit location as described\n\
+below.\n\
+\n\
With no LOCATION, uses current execution address of the selected\n\
stack frame. This is useful for breaking on return to a stack frame.\n\
\n\
THREADNUM is the number from \"info threads\".\n\
CONDITION is a boolean expression.\n\
-\n\
+\n" LOCATION_HELP_STRING "\n\
Multiple breakpoints at one place are permitted, and useful if their\n\
conditions are different.\n\
\n\
@@ -16040,20 +16060,17 @@ This command may be abbreviated \"delete\"."),
&deletelist);

add_com ("clear", class_breakpoint, clear_command, _("\
-Clear breakpoint at specified line or function.\n\
-Argument may be line number, function name, or \"*\" and an address.\n\
-If line number is specified, all breakpoints in that line are cleared.\n\
-If function is specified, breakpoints at beginning of function are cleared.\n\
-If an address is specified, breakpoints at that address are cleared.\n\
+Clear breakpoint at specified location.\n\
+Argument may be a linespec, explicit, or address location as described below.\n\
\n\
With no argument, clears all breakpoints in the line that the selected frame\n\
-is executing in.\n\
-\n\
+is executing in.\n"
+"\n" LOCATION_HELP_STRING "\n\
See also the \"delete\" command which clears breakpoints by number."));
add_com_alias ("cl", "clear", class_breakpoint, 1);

c = add_com ("break", class_breakpoint, break_command, _("\
-Set breakpoint at specified line or function.\n"
+Set breakpoint at specified location.\n"
BREAK_ARGS_HELP ("break")));
set_cmd_completer (c, location_completer);

@@ -16216,7 +16233,7 @@ hardware.)"),
/* Tracepoint manipulation commands. */

c = add_com ("trace", class_breakpoint, trace_command, _("\
-Set a tracepoint at specified line or function.\n\
+Set a tracepoint at specified location.\n\
\n"
BREAK_ARGS_HELP ("trace") "\n\
Do \"help tracepoints\" for info on other tracepoint commands."));
@@ -16228,31 +16245,27 @@ Do \"help tracepoints\" for info on other tracepoint commands."));
add_com_alias ("trac", "trace", class_alias, 1);

c = add_com ("ftrace", class_breakpoint, ftrace_command, _("\
-Set a fast tracepoint at specified line or function.\n\
+Set a fast tracepoint at specified location.\n\
\n"
BREAK_ARGS_HELP ("ftrace") "\n\
Do \"help tracepoints\" for info on other tracepoint commands."));
set_cmd_completer (c, location_completer);

c = add_com ("strace", class_breakpoint, strace_command, _("\
-Set a static tracepoint at specified line, function or marker.\n\
+Set a static tracepoint at location or marker.\n\
\n\
strace [LOCATION] [if CONDITION]\n\
-LOCATION may be a line number, function name, \"*\" and an address,\n\
-or -m MARKER_ID.\n\
-If a line number is specified, probe the marker at start of code\n\
-for that line. If a function is specified, probe the marker at start\n\
-of code for that function. If an address is specified, probe the marker\n\
-at that exact address. If a marker id is specified, probe the marker\n\
-with that name. With no LOCATION, uses current execution address of\n\
-the selected stack frame.\n\
+LOCATION may be a linespec, explicit, or address location (described below) \n\
+or -m MARKER_ID.\n\n\
+If a marker id is specified, probe the marker with that name. With\n\
+no LOCATION, uses current execution address of the selected stack frame.\n\
Static tracepoints accept an extra collect action -- ``collect $_sdata''.\n\
This collects arbitrary user data passed in the probe point call to the\n\
tracing library. You can inspect it when analyzing the trace buffer,\n\
by printing the $_sdata variable like any other convenience variable.\n\
\n\
CONDITION is a boolean expression.\n\
-\n\
+\n" LOCATION_HELP_STRING "\n\
Multiple tracepoints at one place are permitted, and useful if their\n\
conditions are different.\n\
\n\
@@ -16404,11 +16417,10 @@ an instruction at any address within the [START-LOCATION, END-LOCATION]\n\
range (including START-LOCATION and END-LOCATION)."));

c = add_com ("dprintf", class_breakpoint, dprintf_command, _("\
-Set a dynamic printf at specified line or function.\n\
+Set a dynamic printf at specified location.\n\
dprintf location,format string,arg1,arg2,...\n\
-location may be a line number, function name, or \"*\" and an address.\n\
-If a line number is specified, break at start of code for that line.\n\
-If a function is specified, break at start of code for that function."));
+location may be a linespec, explicit, or address location.\n"
+"\n" LOCATION_HELP_STRING));
set_cmd_completer (c, location_completer);

add_setshow_enum_cmd ("dprintf-style", class_support,
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 19d8bb3..6f7e16a 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -6057,9 +6057,9 @@ breakpoints on all threads, or on a particular thread.
@cindex breakpoints and threads
@cindex thread breakpoints
@kindex break @dots{} thread @var{threadno}
-@item break @var{linespec} thread @var{threadno}
-@itemx break @var{linespec} thread @var{threadno} if @dots{}
-@var{linespec} specifies source lines; there are several ways of
+@item break @var{location} thread @var{threadno}
+@itemx break @var{location} thread @var{threadno} if @dots{}
+@var{location} specifies source lines; there are several ways of
writing them (@pxref{Specify Location}), but the effect is always to
specify some source line.

@@ -7485,21 +7485,21 @@ argument of @samp{-}; that argument is preserved in repetition so that
each repetition moves up in the source file.

In general, the @code{list} command expects you to supply zero, one or two
-@dfn{linespecs}. Linespecs specify source lines; there are several ways
+@dfn{locations}. Locations specify source lines; there are several ways
of writing them (@pxref{Specify Location}), but the effect is always
to specify some source line.

Here is a complete description of the possible arguments for @code{list}:

@table @code
-@item list @var{linespec}
-Print lines centered around the line specified by @var{linespec}.
+@item list @var{location}
+Print lines centered around the line specified by @var{location}.

@item list @var{first},@var{last}
Print lines from @var{first} to @var{last}. Both arguments are
-linespecs. When a @code{list} command has two linespecs, and the
-source file of the second linespec is omitted, this refers to
-the same source file as the first linespec.
+locations. When a @code{list} command has two locations, and the
+source file of the second location is omitted, this refers to
+the same source file as the first location.

@item list ,@var{last}
Print lines ending with @var{last}.
@@ -7524,11 +7524,16 @@ As described in the preceding table.

Several @value{GDBN} commands accept arguments that specify a location
of your program's code. Since @value{GDBN} is a source-level
-debugger, a location usually specifies some line in the source code;
-for that reason, locations are also known as @dfn{linespecs}.
+debugger, a location usually specifies some line in the source code.
+Locations may be specified using three different formats:
+linespec locations, explicit locations, or address locations.

-Here are all the different ways of specifying a code location that
-@value{GDBN} understands:
+@subsection Linespec Locations
+@anchor{Linespec Locations}
+
+A @dfn{linespec} is a colon-separated list of source location parameters such
+as file name, function name, etc. Here are all the different ways of
+specifying a linespec:

@table @code
@item @var{linenum}
@@ -7567,25 +7572,93 @@ function name to avoid ambiguity when there are identically named
functions in different source files.

@item @var{label}
-Specifies the line at which the label named @var{label} appears.
-@value{GDBN} searches for the label in the function corresponding to
-the currently selected stack frame. If there is no current selected
-stack frame (for instance, if the inferior is not running), then
-@value{GDBN} will not search for a label.
-
-@item *@var{address}
-Specifies the program address @var{address}. For line-oriented
-commands, such as @code{list} and @code{edit}, this specifies a source
-line that contains @var{address}. For @code{break} and other
-breakpoint oriented commands, this can be used to set breakpoints in
+Specifies the line at which the label named @var{label} appears
+in the function corresponding to the currently selected stack frame.
+If there is no current selected stack frame (for instance, if the inferior
+is not running), then @value{GDBN} will not search for a label.
+
+@cindex breakpoint at static probe point
+@item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
+The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
+applications to embed static probes. @xref{Static Probe Points}, for more
+information on finding and using static probes. This form of linespec
+specifies the location of such a static probe.
+
+If @var{objfile} is given, only probes coming from that shared library
+or executable matching @var{objfile} as a regular expression are considered.
+If @var{provider} is given, then only probes from that provider are considered.
+If several probes match the spec, @value{GDBN} will insert a breakpoint at
+each one of those probes.
+@end table
+
+@subsection Explicit Locations
+@cindex explicit locations
+@anchor{Explicit Locations}
+
+@dfn{Explicit locations} allow the user to directly specify the source
+location's parameters using option-value pairs.
+
+Explicit locations are useful when several functions, labels, or
+file names have the same name (base name for files) in the program's
+sources. In these cases, explicit locations point to the source
+line you meant more accurately and unambiguously. Also, using
+explicit locations might be faster in large programs.
+
+For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
+defined in the file named @file{foo} or the label @code{bar} in a function
+named @code{foo}. @value{GDBN} must search either the file system or
+the symbol table to know.
+
+The list of valid explicit location options is summarized in the
+following table:
+
+@table @code
+@item -source @var{filename}
+The value specifies the source file name. To differentiate between
+files with the same base name, prepend as many directories as is necessary
+to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
+@value{GDBN} will use the first file it finds with the given base
+name. This option requires the use of either @code{-function} or @code{-line}.
+
+@item -function @var{function}
+The value specifies the name of a function. Operations
+on function locations unmodified by other options (such as @code{-label}
+or @code{-line}) refer to the line that begins the body of the function.
+In C, for example, this is the line with the open brace.
+
+@item -label @var{label}
+The value specifies the name of a label. When the function
+name is not specified, the label is searched in the function of the currently
+selected stack frame.
+
+@item -line @var{number}
+The value specifies a line offset for the location. The offset may either
+be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
+the command. When specified without any other options, the line offset is
+relative to the current line.
+@end table
+
+Explicit location options may be abbreviated by omitting any non-unique
+trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
+
+@subsection Address Locations
+@cindex address locations
+@anchor{Address Locations}
+
+@dfn{Address locations} indicate a specific program address. They have
+the generalized form *@var{address}.
+
+For line-oriented commands, such as @code{list} and @code{edit}, this
+specifies a source line that contains @var{address}. For @code{break} and
+other breakpoint-oriented commands, this can be used to set breakpoints in
parts of your program which do not have debugging information or
source files.

Here @var{address} may be any expression valid in the current working
language (@pxref{Languages, working language}) that specifies a code
address. In addition, as a convenience, @value{GDBN} extends the
-semantics of expressions used in locations to cover the situations
-that frequently happen during debugging. Here are the various forms
+semantics of expressions used in locations to cover several situations
+that frequently occur during debugging. Here are the various forms
of @var{address}:

@table @code
@@ -7610,22 +7683,6 @@ specify the function unambiguously, e.g., if there are several
functions with identical names in different source files.
@end table

-@cindex breakpoint at static probe point
-@item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
-The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
-applications to embed static probes. @xref{Static Probe Points}, for more
-information on finding and using static probes. This form of linespec
-specifies the location of such a static probe.
-
-If @var{objfile} is given, only probes coming from that shared library
-or executable matching @var{objfile} as a regular expression are considered.
-If @var{provider} is given, then only probes from that provider are considered.
-If several probes match the spec, @value{GDBN} will insert a breakpoint at
-each one of those probes.
-
-@end table
-
-
@node Edit
@section Editing Source Files
@cindex editing source files
@@ -7943,9 +8000,9 @@ well as hex.

@table @code
@kindex info line
-@item info line @var{linespec}
+@item info line @var{location}
Print the starting and ending addresses of the compiled code for
-source line @var{linespec}. You can specify source lines in any of
+source line @var{location}. You can specify source lines in any of
the ways documented in @ref{Specify Location}.
@end table

@@ -7963,7 +8020,7 @@ Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
@noindent
@cindex code address and its source line
We can also inquire (using @code{*@var{addr}} as the form for
-@var{linespec}) what source line covers a particular address:
+@var{location}) what source line covers a particular address:
@smallexample
(@value{GDBP}) info line *0x63ff
Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
@@ -8073,7 +8130,7 @@ Dump of assembler code from 0x400281 to 0x40028b:
End of assembler dump.
@end smallexample

-Addresses cannot be specified as a linespec (@pxref{Specify Location}).
+Addresses cannot be specified as a location (@pxref{Specify Location}).
So, for example, if you want to disassemble function @code{bar}
in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
and not @samp{disassemble foo.c:bar}.
@@ -11714,9 +11771,9 @@ argument processing and the beginning of @var{macro} for non C-like macros where
the macro may begin with a hyphen.

@kindex info macros
-@item info macros @var{linespec}
+@item info macros @var{location}
Show all macro definitions that are in effect at the location specified
-by @var{linespec}, and describe the source location or compiler
+by @var{location}, and describe the source location or compiler
command-line where those definitions were established.

@kindex macro define
@@ -12021,12 +12078,11 @@ conditions and actions.
@kindex trace
@item trace @var{location}
The @code{trace} command is very similar to the @code{break} command.
-Its argument @var{location} can be a source line, a function name, or
-an address in the target program. @xref{Specify Location}. The
-@code{trace} command defines a tracepoint, which is a point in the
-target program where the debugger will briefly stop, collect some
-data, and then allow the program to continue. Setting a tracepoint or
-changing its actions takes effect immediately if the remote stub
+Its argument @var{location} can be any valid location.
+@xref{Specify Location}. The @code{trace} command defines a tracepoint,
+which is a point in the target program where the debugger will briefly stop,
+collect some data, and then allow the program to continue. Setting a tracepoint
+or changing its actions takes effect immediately if the remote stub
supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
in tracing}).
If remote stub doesn't support the @samp{InstallInTrace} feature, all
@@ -15906,14 +15962,14 @@ from the current task to the given task.
#4 0x804aacc in un () at un.adb:5
@end smallexample

-@item break @var{linespec} task @var{taskno}
-@itemx break @var{linespec} task @var{taskno} if @dots{}
+@item break @var{location} task @var{taskno}
+@itemx break @var{location} task @var{taskno} if @dots{}
@cindex breakpoints and tasks, in Ada
@cindex task breakpoints, in Ada
@kindex break @dots{} task @var{taskno}@r{ (Ada)}
These commands are like the @code{break @dots{} thread @dots{}}
command (@pxref{Thread Stops}). The
-@var{linespec} argument specifies source lines, as described
+@var{location} argument specifies source lines, as described
in @ref{Specify Location}.

Use the qualifier @samp{task @var{taskno}} with a breakpoint command
@@ -16841,20 +16897,17 @@ an address of your own choosing, with the following commands:
@table @code
@kindex jump
@kindex j @r{(@code{jump})}
-@item jump @var{linespec}
-@itemx j @var{linespec}
-@itemx jump @var{location}
+@item jump @var{location}
@itemx j @var{location}
-Resume execution at line @var{linespec} or at address given by
-@var{location}. Execution stops again immediately if there is a
-breakpoint there. @xref{Specify Location}, for a description of the
-different forms of @var{linespec} and @var{location}. It is common
+Resume execution at @var{location}. Execution stops again immediately
+if there is a breakpoint there. @xref{Specify Location}, for a description
+of the different forms of @var{location}. It is common
practice to use the @code{tbreak} command in conjunction with
@code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.

The @code{jump} command does not change the current stack frame, or
the stack pointer, or the contents of any memory location or any
-register other than the program counter. If line @var{linespec} is in
+register other than the program counter. If @var{location} is in
a different function from the one currently executing, the results may
be bizarre if the two functions expect different patterns of arguments or
of local variables. For this reason, the @code{jump} command requests
@@ -26674,6 +26727,7 @@ N.A.

@subheading The @code{-break-insert} Command
@findex -break-insert
+@anchor{-break-insert}

@subsubheading Synopsis

@@ -26686,16 +26740,35 @@ N.A.
@noindent
If specified, @var{location}, can be one of:

-@itemize @bullet
-@item function
-@c @item +offset
-@c @item -offset
-@c @item linenum
-@item filename:linenum
-@item filename:function
-@item *address
-@end itemize
+@table @var
+@item linespec location
+A linespec location. @xref{Linespec Locations}.

+@item explicit location
+An explicit location. @sc{gdb/mi} explicit locations are
+analogous to the CLI's explicit locations using the option names
+listed below. @xref{Explicit Locations}.
+
+@table @samp
+@item --source @var{filename}
+The source file name of the location. This option requires the use
+of either @samp{--function} or @samp{--line}.
+
+@item --function @var{function}
+The name of a function or method.
+
+@item --label @var{label}
+The name of a label.
+
+@item --line @var{lineoffset}
+An absolute or relative line offset from the start of the location.
+@end table
+
+@item address location
+An address location, *@var{address}. @xref{Address Locations}.
+@end table
+
+@noindent
The possible optional parameters of this command are:

@table @samp
@@ -26787,17 +26860,8 @@ times="0"@}]@}
@end smallexample

@noindent
-If specified, @var{location}, can be one of:
-
-@itemize @bullet
-@item @var{function}
-@c @item +offset
-@c @item -offset
-@c @item @var{linenum}
-@item @var{filename}:@var{linenum}
-@item @var{filename}:function
-@item *@var{address}
-@end itemize
+If supplied, @var{location} may be specified the same way as for
+the @code{-break-insert} command. @xref{-break-insert}.

The possible optional parameters of this command are:

diff --git a/gdb/testsuite/gdb.base/help.exp b/gdb/testsuite/gdb.base/help.exp
index 565e339..22e6aa3 100644
--- a/gdb/testsuite/gdb.base/help.exp
+++ b/gdb/testsuite/gdb.base/help.exp
@@ -58,7 +58,7 @@ test_class_help "user-defined" {
}

# Test help of an abbreviated command. "break" is picked at random.
-set help_breakpoint_text "Set breakpoint at specified line or function\..*"
+set help_breakpoint_text "Set breakpoint at specified location\..*"
# test help breakpoint "b" abbreviation
gdb_test "help b" $help_breakpoint_text "help breakpoint \"b\" abbreviation"
# test help breakpoint "br" abbreviation