To request debugging information, specify the @samp{-g} option when you run
the compiler.
-Most compilers do not include information about preprocessor macros in
-the debugging information if you specify the @option{-g} flag alone,
-because this information is rather large. Version 3.1 of @value{NGCC},
-the @sc{gnu} C compiler, provides macro information if you specify the
-options @option{-gdwarf-2} and @option{-g3}; the former option requests
-debugging information in the Dwarf 2 format, and the latter requests
-``extra information''. In the future, we hope to find more compact ways
-to represent macro information, so that it can be included with
-@option{-g} alone.
-
-Many C compilers are unable to handle the @samp{-g} and @samp{-O}
-options together. Using those compilers, you cannot generate optimized
+Programs that are to be shipped to your customers are compiled with
+optimizations, using the @samp{-O} compiler option. However, many
+compilers are unable to handle the @samp{-g} and @samp{-O} options
+together. Using those compilers, you cannot generate optimized
executables containing debugging information.
-@value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
+@value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
without @samp{-O}, making it possible to debug optimized code. We
recommend that you @emph{always} use @samp{-g} whenever you compile a
program. You may think your program is correct, but there is no sense
@w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
format; if your @sc{gnu} C compiler has this option, do not use it.
+@value{GDBN} knows about preprocessor macros and can show you their
+expansion (@pxref{Macros}). Most compilers do not include information
+about preprocessor macros in the debugging information if you specify
+the @option{-g} flag alone, because this information is rather large.
+Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
+provides macro information if you specify the options
+@option{-gdwarf-2} and @option{-g3}; the former option requests
+debugging information in the Dwarf 2 format, and the latter requests
+``extra information''. In the future, we hope to find more compact
+ways to represent macro information, so that it can be included with
+@option{-g} alone.
+
@need 2000
@node Starting
@section Starting your program
@cindex native @sc{djgpp} debugging
@cindex MS-DOS-specific commands
-@sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
+@cindex DPMI
+@sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
top of real-mode DOS systems and their emulations.
@cindex physical address from linear address
@item info dos address-pte @var{addr}
This command displays the Page Table entry for a specified linear
-address. The argument linear address @var{addr} should already have the
-appropriate segment's base address added to it, because this command
-accepts addresses which may belong to @emph{any} segment. For
-example, here's how to display the Page Table entry for the page where
-the variable @code{i} is stored:
+address. The argument @var{addr} is a linear address which should
+already have the appropriate segment's base address added to it,
+because this command accepts addresses which may belong to @emph{any}
+segment. For example, here's how to display the Page Table entry for
+the page where a variable @code{i} is stored:
@smallexample
@exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
@noindent
This says that @code{i} is stored at offset @code{0xd30} from the page
-whose physical base address is @code{0x02698000}, and prints all the
+whose physical base address is @code{0x02698000}, and shows all the
attributes of that page.
Note that you must cast the addresses of variables to a @code{char *},
@noindent
(The @code{+ 3} offset is because the transfer buffer's address is the
-3rd member of the @code{_go32_info_block} structure.) The output of
-this command clearly shows that addresses in conventional memory are
-mapped 1:1, i.e.@: the physical and linear addresses are identical.
+3rd member of the @code{_go32_info_block} structure.) The output
+clearly shows that this DPMI server maps the addresses in conventional
+memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
+linear (@code{0x29110}) addresses are identical.
This command is supported only with some DPMI servers.
@end table