компилятор C и C ++ проекта GNU (GNU project C and C++ compiler)
Параметры подробно (Options detail)
Debugging Your Program
To tell GCC to emit extra information for use by a debugger, in
almost all cases you need only to add -g to your other options.
GCC allows you to use -g with -O. The shortcuts taken by
optimized code may occasionally be surprising: some variables you
declared may not exist at all; flow of control may briefly move
where you did not expect it; some statements may not be executed
because they compute constant results or their values are already
at hand; some statements may execute in different places because
they have been moved out of loops. Nevertheless it is possible
to debug optimized output. This makes it reasonable to use the
optimizer for programs that might have bugs.
If you are not using some other optimization option, consider
using -Og with -g. With no -O option at all, some compiler
passes that collect information useful for debugging do not run
at all, so that -Og may result in a better debugging experience.
-g Produce debugging information in the operating system's
native format (stabs, COFF, XCOFF, or DWARF). GDB can work
with this debugging information.
On most systems that use stabs format, -g enables use of
extra debugging information that only GDB can use; this extra
information makes debugging work better in GDB but probably
makes other debuggers crash or refuse to read the program.
If you want to control for certain whether to generate the
extra information, use -gstabs+, -gstabs, -gxcoff+, -gxcoff,
or -gvms (see below).
-ggdb
Produce debugging information for use by GDB. This means to
use the most expressive format available (DWARF, stabs, or
the native format if neither of those are supported),
including GDB extensions if at all possible.
-gdwarf
-gdwarf-version
Produce debugging information in DWARF format (if that is
supported). The value of version may be either 2, 3, 4 or 5;
the default version for most targets is 4. DWARF Version 5
is only experimental.
Note that with DWARF Version 2, some ports require and always
use some non-conflicting DWARF 3 extensions in the unwind
tables.
Version 4 may require GDB 7.0 and -fvar-tracking-assignments
for maximum benefit.
GCC no longer supports DWARF Version 1, which is
substantially different than Version 2 and later. For
historical reasons, some other DWARF-related options such as
-fno-dwarf2-cfi-asm) retain a reference to DWARF Version 2 in
their names, but apply to all currently-supported versions of
DWARF.
-gstabs
Produce debugging information in stabs format (if that is
supported), without GDB extensions. This is the format used
by DBX on most BSD systems. On MIPS, Alpha and System V
Release 4 systems this option produces stabs debugging output
that is not understood by DBX. On System V Release 4 systems
this option requires the GNU assembler.
-gstabs+
Produce debugging information in stabs format (if that is
supported), using GNU extensions understood only by the GNU
debugger (GDB). The use of these extensions is likely to
make other debuggers crash or refuse to read the program.
-gxcoff
Produce debugging information in XCOFF format (if that is
supported). This is the format used by the DBX debugger on
IBM RS/6000 systems.
-gxcoff+
Produce debugging information in XCOFF format (if that is
supported), using GNU extensions understood only by the GNU
debugger (GDB). The use of these extensions is likely to
make other debuggers crash or refuse to read the program, and
may cause assemblers other than the GNU assembler (GAS) to
fail with an error.
-gvms
Produce debugging information in Alpha/VMS debug format (if
that is supported). This is the format used by DEBUG on
Alpha/VMS systems.
-glevel
-ggdblevel
-gstabslevel
-gxcofflevel
-gvmslevel
Request debugging information and also use level to specify
how much information. The default level is 2.
Level 0 produces no debug information at all. Thus, -g0
negates -g.
Level 1 produces minimal information, enough for making
backtraces in parts of the program that you don't plan to
debug. This includes descriptions of functions and external
variables, and line number tables, but no information about
local variables.
Level 3 includes extra information, such as all the macro
definitions present in the program. Some debuggers support
macro expansion when you use -g3.
If you use multiple -g options, with or without level
numbers, the last such option is the one that is effective.
-gdwarf does not accept a concatenated debug level, to avoid
confusion with -gdwarf-level. Instead use an additional
-glevel option to change the debug level for DWARF.
-feliminate-unused-debug-symbols
Produce debugging information in stabs format (if that is
supported), for only symbols that are actually used.
-femit-class-debug-always
Instead of emitting debugging information for a C++ class in
only one object file, emit it in all object files using the
class. This option should be used only with debuggers that
are unable to handle the way GCC normally emits debugging
information for classes because using this option increases
the size of debugging information by as much as a factor of
two.
-fno-merge-debug-strings
Direct the linker to not merge together strings in the
debugging information that are identical in different object
files. Merging is not supported by all assemblers or
linkers. Merging decreases the size of the debug information
in the output file at the cost of increasing link processing
time. Merging is enabled by default.
-fdebug-prefix-map=old=new
When compiling files residing in directory old, record
debugging information describing them as if the files resided
in directory new instead. This can be used to replace a
build-time path with an install-time path in the debug info.
It can also be used to change an absolute path to a relative
path by using . for new. This can give more reproducible
builds, which are location independent, but may require an
extra command to tell GDB where to find the source files. See
also -ffile-prefix-map.
-fvar-tracking
Run variable tracking pass. It computes where variables are
stored at each position in code. Better debugging
information is then generated (if the debugging information
format supports this information).
It is enabled by default when compiling with optimization
(-Os, -O, -O2, ...), debugging information (-g) and the debug
info format supports it.
-fvar-tracking-assignments
Annotate assignments to user variables early in the
compilation and attempt to carry the annotations over
throughout the compilation all the way to the end, in an
attempt to improve debug information while optimizing. Use
of -gdwarf-4 is recommended along with it.
It can be enabled even if var-tracking is disabled, in which
case annotations are created and maintained, but discarded at
the end. By default, this flag is enabled together with
-fvar-tracking, except when selective scheduling is enabled.
-gsplit-dwarf
Separate as much DWARF debugging information as possible into
a separate output file with the extension .dwo. This option
allows the build system to avoid linking files with debug
information. To be useful, this option requires a debugger
capable of reading .dwo files.
-gdescribe-dies
Add description attributes to some DWARF DIEs that have no
name attribute, such as artificial variables, external
references and call site parameter DIEs.
-gpubnames
Generate DWARF ".debug_pubnames" and ".debug_pubtypes"
sections.
-ggnu-pubnames
Generate ".debug_pubnames" and ".debug_pubtypes" sections in
a format suitable for conversion into a GDB index. This
option is only useful with a linker that can produce GDB
index version 7.
-fdebug-types-section
When using DWARF Version 4 or higher, type DIEs can be put
into their own ".debug_types" section instead of making them
part of the ".debug_info" section. It is more efficient to
put them in a separate comdat section since the linker can
then remove duplicates. But not all DWARF consumers support
".debug_types" sections yet and on some objects
".debug_types" produces larger instead of smaller debugging
information.
-grecord-gcc-switches
-gno-record-gcc-switches
This switch causes the command-line options used to invoke
the compiler that may affect code generation to be appended
to the DW_AT_producer attribute in DWARF debugging
information. The options are concatenated with spaces
separating them from each other and from the compiler
version. It is enabled by default. See also
-frecord-gcc-switches for another way of storing compiler
options into the object file.
-gstrict-dwarf
Disallow using extensions of later DWARF standard version
than selected with -gdwarf-version. On most targets using
non-conflicting DWARF extensions from later standard versions
is allowed.
-gno-strict-dwarf
Allow using extensions of later DWARF standard version than
selected with -gdwarf-version.
-gas-loc-support
Inform the compiler that the assembler supports ".loc"
directives. It may then use them for the assembler to
generate DWARF2+ line number tables.
This is generally desirable, because assembler-generated
line-number tables are a lot more compact than those the
compiler can generate itself.
This option will be enabled by default if, at GCC configure
time, the assembler was found to support such directives.
-gno-as-loc-support
Force GCC to generate DWARF2+ line number tables internally,
if DWARF2+ line number tables are to be generated.
gas-locview-support
Inform the compiler that the assembler supports "view"
assignment and reset assertion checking in ".loc" directives.
This option will be enabled by default if, at GCC configure
time, the assembler was found to support them.
gno-as-locview-support
Force GCC to assign view numbers internally, if
-gvariable-location-views are explicitly requested.
-gcolumn-info
-gno-column-info
Emit location column information into DWARF debugging
information, rather than just file and line. This option is
enabled by default.
-gstatement-frontiers
-gno-statement-frontiers
This option causes GCC to create markers in the internal
representation at the beginning of statements, and to keep
them roughly in place throughout compilation, using them to
guide the output of "is_stmt" markers in the line number
table. This is enabled by default when compiling with
optimization (-Os, -O, -O2, ...), and outputting DWARF 2
debug information at the normal level.
-gvariable-location-views
-gvariable-location-views=incompat5
-gno-variable-location-views
Augment variable location lists with progressive view numbers
implied from the line number table. This enables debug
information consumers to inspect state at certain points of
the program, even if no instructions associated with the
corresponding source locations are present at that point. If
the assembler lacks support for view numbers in line number
tables, this will cause the compiler to emit the line number
table, which generally makes them somewhat less compact. The
augmented line number tables and location lists are fully
backward-compatible, so they can be consumed by debug
information consumers that are not aware of these
augmentations, but they won't derive any benefit from them
either.
This is enabled by default when outputting DWARF 2 debug
information at the normal level, as long as there is
assembler support, -fvar-tracking-assignments is enabled and
-gstrict-dwarf is not. When assembler support is not
available, this may still be enabled, but it will force GCC
to output internal line number tables, and if
-ginternal-reset-location-views is not enabled, that will
most certainly lead to silently mismatching location views.
There is a proposed representation for view numbers that is
not backward compatible with the location list format
introduced in DWARF 5, that can be enabled with
-gvariable-location-views=incompat5. This option may be
removed in the future, is only provided as a reference
implementation of the proposed representation. Debug
information consumers are not expected to support this
extended format, and they would be rendered unable to decode
location lists using it.
-ginternal-reset-location-views
-gno-internal-reset-location-views
Attempt to determine location views that can be omitted from
location view lists. This requires the compiler to have very
accurate insn length estimates, which isn't always the case,
and it may cause incorrect view lists to be generated
silently when using an assembler that does not support
location view lists. The GNU assembler will flag any such
error as a "view number mismatch". This is only enabled on
ports that define a reliable estimation function.
-ginline-points
-gno-inline-points
Generate extended debug information for inlined functions.
Location view tracking markers are inserted at inlined entry
points, so that address and view numbers can be computed and
output in debug information. This can be enabled
independently of location views, in which case the view
numbers won't be output, but it can only be enabled along
with statement frontiers, and it is only enabled by default
if location views are enabled.
-gz[=type]
Produce compressed debug sections in DWARF format, if that is
supported. If type is not given, the default type depends on
the capabilities of the assembler and linker used. type may
be one of none (don't compress debug sections), zlib (use
zlib compression in ELF gABI format), or zlib-gnu (use zlib
compression in traditional GNU format). If the linker
doesn't support writing compressed debug sections, the option
is rejected. Otherwise, if the assembler does not support
them, -gz is silently ignored when producing object files.
-femit-struct-debug-baseonly
Emit debug information for struct-like types only when the
base name of the compilation source file matches the base
name of file in which the struct is defined.
This option substantially reduces the size of debugging
information, but at significant potential loss in type
information to the debugger. See -femit-struct-debug-reduced
for a less aggressive option. See
-femit-struct-debug-detailed for more detailed control.
This option works only with DWARF debug output.
-femit-struct-debug-reduced
Emit debug information for struct-like types only when the
base name of the compilation source file matches the base
name of file in which the type is defined, unless the struct
is a template or defined in a system header.
This option significantly reduces the size of debugging
information, with some potential loss in type information to
the debugger. See -femit-struct-debug-baseonly for a more
aggressive option. See -femit-struct-debug-detailed for more
detailed control.
This option works only with DWARF debug output.
-femit-struct-debug-detailed[=spec-list]
Specify the struct-like types for which the compiler
generates debug information. The intent is to reduce
duplicate struct debug information between different object
files within the same program.
This option is a detailed version of
-femit-struct-debug-reduced and -femit-struct-debug-baseonly,
which serves for most needs.
A specification has the
syntax[dir:|ind:][ord:|gen:](any|sys|base|none)
The optional first word limits the specification to structs
that are used directly (dir:) or used indirectly (ind:). A
struct type is used directly when it is the type of a
variable, member. Indirect uses arise through pointers to
structs. That is, when use of an incomplete struct is valid,
the use is indirect. An example is struct one direct; struct
two * indirect;.
The optional second word limits the specification to ordinary
structs (ord:) or generic structs (gen:). Generic structs
are a bit complicated to explain. For C++, these are non-
explicit specializations of template classes, or non-template
classes within the above. Other programming languages have
generics, but -femit-struct-debug-detailed does not yet
implement them.
The third word specifies the source files for those structs
for which the compiler should emit debug information. The
values none and any have the normal meaning. The value base
means that the base of name of the file in which the type
declaration appears must match the base of the name of the
main compilation file. In practice, this means that when
compiling foo.c, debug information is generated for types
declared in that file and foo.h, but not other header files.
The value sys means those types satisfying base or declared
in system or compiler headers.
You may need to experiment to determine the best settings for
your application.
The default is -femit-struct-debug-detailed=all.
This option works only with DWARF debug output.
-fno-dwarf2-cfi-asm
Emit DWARF unwind info as compiler generated ".eh_frame"
section instead of using GAS ".cfi_*" directives.
-fno-eliminate-unused-debug-types
Normally, when producing DWARF output, GCC avoids producing
debug symbol output for types that are nowhere used in the
source file being compiled. Sometimes it is useful to have
GCC emit debugging information for all types declared in a
compilation unit, regardless of whether or not they are
actually used in that compilation unit, for example if, in
the debugger, you want to cast a value to a type that is not
actually used in your program (but is declared). More often,
however, this results in a significant amount of wasted
space.
