(gcc.info.gz) Debugging Options
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(gcc.info.gz) Warning Options
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3.9 Options for Debugging Your Program or GCC
=============================================
GCC has various special options that are used for debugging either your
program or GCC:
`-g'
Produce debugging information in the operating system's native
format (stabs, COFF, XCOFF, or DWARF 2). 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 will probably make 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).
GCC allows you to use `-g' with `-O'. The shortcuts taken by
optimized code may occasionally produce surprising results: 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
were already at hand; some statements may execute in different
places because they were moved out of loops.
Nevertheless it proves possible to debug optimized output. This
makes it reasonable to use the optimizer for programs that might
have bugs.
The following options are useful when GCC is generated with the
capability for more than one debugging format.
`-ggdb'
Produce debugging information for use by GDB. This means to use
the most expressive format available (DWARF 2, stabs, or the
native format if neither of those are supported), including GDB
extensions if at all possible.
`-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 which is not
understood by DBX or SDB. On System V Release 4 systems this
option requires the GNU assembler.
`-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 will increase the size of
debugging information by as much as a factor of two.
`-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.
`-gcoff'
Produce debugging information in COFF format (if that is
supported). This is the format used by SDB on most System V
systems prior to System V Release 4.
`-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.
`-gdwarf-VERSION'
Produce debugging information in DWARF format (if that is
supported). This is the format used by DBX on IRIX 6. The value
of VERSION may be either 2 or 3; the default version is 3.
Note that with DWARF version 2 some ports require, and will always
use, some non-conflicting DWARF 3 extensions in the unwind tables.
`-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'.
`-gvms'
Produce debugging information in VMS debug format (if that is
supported). This is the format used by DEBUG on VMS systems.
`-gLEVEL'
`-ggdbLEVEL'
`-gstabsLEVEL'
`-gcoffLEVEL'
`-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, but no
information about local variables and no line numbers.
Level 3 includes extra information, such as all the macro
definitions present in the program. Some debuggers support macro
expansion when you use `-g3'.
`-gdwarf-2' does not accept a concatenated debug level, because
GCC used to support an option `-gdwarf' that meant to generate
debug information in version 1 of the DWARF format (which is very
different from version 2), and it would have been too confusing.
That debug format is long obsolete, but the option cannot be
changed now. Instead use an additional `-gLEVEL' option to change
the debug level for DWARF.
`-gtoggle'
Turn off generation of debug info, if leaving out this option
would have generated it, or turn it on at level 2 otherwise. The
position of this argument in the command line does not matter, it
takes effect after all other options are processed, and it does so
only once, no matter how many times it is given. This is mainly
intended to be used with `-fcompare-debug'.
`-fdump-final-insns[=FILE]'
Dump the final internal representation (RTL) to FILE. If the
optional argument is omitted (or if FILE is `.'), the name of the
dump file will be determined by appending `.gkd' to the
compilation output file name.
`-fcompare-debug[=OPTS]'
If no error occurs during compilation, run the compiler a second
time, adding OPTS and `-fcompare-debug-second' to the arguments
passed to the second compilation. Dump the final internal
representation in both compilations, and print an error if they
differ.
If the equal sign is omitted, the default `-gtoggle' is used.
The environment variable `GCC_COMPARE_DEBUG', if defined, non-empty
and nonzero, implicitly enables `-fcompare-debug'. If
`GCC_COMPARE_DEBUG' is defined to a string starting with a dash,
then it is used for OPTS, otherwise the default `-gtoggle' is used.
`-fcompare-debug=', with the equal sign but without OPTS, is
equivalent to `-fno-compare-debug', which disables the dumping of
the final representation and the second compilation, preventing
even `GCC_COMPARE_DEBUG' from taking effect.
To verify full coverage during `-fcompare-debug' testing, set
`GCC_COMPARE_DEBUG' to say `-fcompare-debug-not-overridden', which
GCC will reject as an invalid option in any actual compilation
(rather than preprocessing, assembly or linking). To get just a
warning, setting `GCC_COMPARE_DEBUG' to `-w%n-fcompare-debug not
overridden' will do.
`-fcompare-debug-second'
This option is implicitly passed to the compiler for the second
compilation requested by `-fcompare-debug', along with options to
silence warnings, and omitting other options that would cause
side-effect compiler outputs to files or to the standard output.
Dump files and preserved temporary files are renamed so as to
contain the `.gk' additional extension during the second
compilation, to avoid overwriting those generated by the first.
When this option is passed to the compiler driver, it causes the
_first_ compilation to be skipped, which makes it useful for little
other than debugging the compiler proper.
`-feliminate-dwarf2-dups'
Compress DWARF2 debugging information by eliminating duplicated
information about each symbol. This option only makes sense when
generating DWARF2 debugging information with `-gdwarf-2'.
`-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 was 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 2.
`-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 was 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 2.
`-femit-struct-debug-detailed[=SPEC-LIST]'
Specify the struct-like types for which the compiler will generate
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 will serve 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 would be legal, 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 will 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 types declared in `foo.c' and `foo.h'
will have debug information, but types declared in other header
will not. 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 2.
`-fno-merge-debug-strings'
Direct the linker to not merge together strings in the debugging
information which 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 in directory `OLD', record debugging
information describing them as in `NEW' instead.
`-fno-dwarf2-cfi-asm'
Emit DWARF 2 unwind info as compiler generated `.eh_frame' section
instead of using GAS `.cfi_*' directives.
`-p'
Generate extra code to write profile information suitable for the
analysis program `prof'. You must use this option when compiling
the source files you want data about, and you must also use it when
linking.
`-pg'
Generate extra code to write profile information suitable for the
analysis program `gprof'. You must use this option when compiling
the source files you want data about, and you must also use it when
linking.
`-Q'
Makes the compiler print out each function name as it is compiled,
and print some statistics about each pass when it finishes.
`-ftime-report'
Makes the compiler print some statistics about the time consumed
by each pass when it finishes.
`-fmem-report'
Makes the compiler print some statistics about permanent memory
allocation when it finishes.
`-fpre-ipa-mem-report'
`-fpost-ipa-mem-report'
Makes the compiler print some statistics about permanent memory
allocation before or after interprocedural optimization.
`-fprofile-arcs'
Add code so that program flow "arcs" are instrumented. During
execution the program records how many times each branch and call
is executed and how many times it is taken or returns. When the
compiled program exits it saves this data to a file called
`AUXNAME.gcda' for each source file. The data may be used for
profile-directed optimizations (`-fbranch-probabilities'), or for
test coverage analysis (`-ftest-coverage'). Each object file's
AUXNAME is generated from the name of the output file, if
explicitly specified and it is not the final executable, otherwise
it is the basename of the source file. In both cases any suffix
is removed (e.g. `foo.gcda' for input file `dir/foo.c', or
`dir/foo.gcda' for output file specified as `-o dir/foo.o').
Cross-profiling.
`--coverage'
This option is used to compile and link code instrumented for
coverage analysis. The option is a synonym for `-fprofile-arcs'
`-ftest-coverage' (when compiling) and `-lgcov' (when linking).
See the documentation for those options for more details.
* Compile the source files with `-fprofile-arcs' plus
optimization and code generation options. For test coverage
analysis, use the additional `-ftest-coverage' option. You
do not need to profile every source file in a program.
* Link your object files with `-lgcov' or `-fprofile-arcs' (the
latter implies the former).
* Run the program on a representative workload to generate the
arc profile information. This may be repeated any number of
times. You can run concurrent instances of your program, and
provided that the file system supports locking, the data
files will be correctly updated. Also `fork' calls are
detected and correctly handled (double counting will not
happen).
* For profile-directed optimizations, compile the source files
again with the same optimization and code generation options
plus `-fbranch-probabilities' ( Options that Control
Optimization Optimize Options.).
* For test coverage analysis, use `gcov' to produce human
readable information from the `.gcno' and `.gcda' files.
Refer to the `gcov' documentation for further information.
With `-fprofile-arcs', for each function of your program GCC
creates a program flow graph, then finds a spanning tree for the
graph. Only arcs that are not on the spanning tree have to be
instrumented: the compiler adds code to count the number of times
that these arcs are executed. When an arc is the only exit or
only entrance to a block, the instrumentation code can be added to
the block; otherwise, a new basic block must be created to hold
the instrumentation code.
`-ftest-coverage'
Produce a notes file that the `gcov' code-coverage utility (
`gcov'--a Test Coverage Program Gcov.) can use to show program
coverage. Each source file's note file is called `AUXNAME.gcno'.
Refer to the `-fprofile-arcs' option above for a description of
AUXNAME and instructions on how to generate test coverage data.
Coverage data will match the source files more closely, if you do
not optimize.
`-fdbg-cnt-list'
Print the name and the counter upperbound for all debug counters.
`-fdbg-cnt=COUNTER-VALUE-LIST'
Set the internal debug counter upperbound. COUNTER-VALUE-LIST is a
comma-separated list of NAME:VALUE pairs which sets the upperbound
of each debug counter NAME to VALUE. All debug counters have the
initial upperbound of UINT_MAX, thus dbg_cnt() returns true always
unless the upperbound is set by this option. e.g. With
-fdbg-cnt=dce:10,tail_call:0 dbg_cnt(dce) will return true only
for first 10 invocations and dbg_cnt(tail_call) will return false
always.
`-dLETTERS'
`-fdump-rtl-PASS'
Says to make debugging dumps during compilation at times specified
by LETTERS. This is used for debugging the RTL-based passes of
the compiler. The file names for most of the dumps are made by
appending a pass number and a word to the DUMPNAME. DUMPNAME is
generated from the name of the output file, if explicitly
specified and it is not an executable, otherwise it is the
basename of the source file. These switches may have different
effects when `-E' is used for preprocessing.
Debug dumps can be enabled with a `-fdump-rtl' switch or some `-d'
option LETTERS. Here are the possible letters for use in PASS and
LETTERS, and their meanings:
`-fdump-rtl-alignments'
Dump after branch alignments have been computed.
`-fdump-rtl-asmcons'
Dump after fixing rtl statements that have unsatisfied in/out
constraints.
`-fdump-rtl-auto_inc_dec'
Dump after auto-inc-dec discovery. This pass is only run on
architectures that have auto inc or auto dec instructions.
`-fdump-rtl-barriers'
Dump after cleaning up the barrier instructions.
`-fdump-rtl-bbpart'
Dump after partitioning hot and cold basic blocks.
`-fdump-rtl-bbro'
Dump after block reordering.
`-fdump-rtl-btl1'
`-fdump-rtl-btl2'
`-fdump-rtl-btl1' and `-fdump-rtl-btl2' enable dumping after
the two branch target load optimization passes.
`-fdump-rtl-bypass'
Dump after jump bypassing and control flow optimizations.
`-fdump-rtl-combine'
Dump after the RTL instruction combination pass.
`-fdump-rtl-compgotos'
Dump after duplicating the computed gotos.
`-fdump-rtl-ce1'
`-fdump-rtl-ce2'
`-fdump-rtl-ce3'
`-fdump-rtl-ce1', `-fdump-rtl-ce2', and `-fdump-rtl-ce3'
enable dumping after the three if conversion passes.
`-fdump-rtl-cprop_hardreg'
Dump after hard register copy propagation.
`-fdump-rtl-csa'
Dump after combining stack adjustments.
`-fdump-rtl-cse1'
`-fdump-rtl-cse2'
`-fdump-rtl-cse1' and `-fdump-rtl-cse2' enable dumping after
the two common sub-expression elimination passes.
`-fdump-rtl-dce'
Dump after the standalone dead code elimination passes.
`-fdump-rtl-dbr'
Dump after delayed branch scheduling.
`-fdump-rtl-dce1'
`-fdump-rtl-dce2'
`-fdump-rtl-dce1' and `-fdump-rtl-dce2' enable dumping after
the two dead store elimination passes.
`-fdump-rtl-eh'
Dump after finalization of EH handling code.
`-fdump-rtl-eh_ranges'
Dump after conversion of EH handling range regions.
`-fdump-rtl-expand'
Dump after RTL generation.
`-fdump-rtl-fwprop1'
`-fdump-rtl-fwprop2'
`-fdump-rtl-fwprop1' and `-fdump-rtl-fwprop2' enable dumping
after the two forward propagation passes.
`-fdump-rtl-gcse1'
`-fdump-rtl-gcse2'
`-fdump-rtl-gcse1' and `-fdump-rtl-gcse2' enable dumping
after global common subexpression elimination.
`-fdump-rtl-init-regs'
Dump after the initialization of the registers.
`-fdump-rtl-initvals'
Dump after the computation of the initial value sets.
`-fdump-rtl-into_cfglayout'
Dump after converting to cfglayout mode.
`-fdump-rtl-ira'
Dump after iterated register allocation.
`-fdump-rtl-jump'
Dump after the second jump optimization.
`-fdump-rtl-loop2'
`-fdump-rtl-loop2' enables dumping after the rtl loop
optimization passes.
`-fdump-rtl-mach'
Dump after performing the machine dependent reorganization
pass, if that pass exists.
`-fdump-rtl-mode_sw'
Dump after removing redundant mode switches.
`-fdump-rtl-rnreg'
Dump after register renumbering.
`-fdump-rtl-outof_cfglayout'
Dump after converting from cfglayout mode.
`-fdump-rtl-peephole2'
Dump after the peephole pass.
`-fdump-rtl-postreload'
Dump after post-reload optimizations.
`-fdump-rtl-pro_and_epilogue'
Dump after generating the function pro and epilogues.
`-fdump-rtl-regmove'
Dump after the register move pass.
`-fdump-rtl-sched1'
`-fdump-rtl-sched2'
`-fdump-rtl-sched1' and `-fdump-rtl-sched2' enable dumping
after the basic block scheduling passes.
`-fdump-rtl-see'
Dump after sign extension elimination.
`-fdump-rtl-seqabstr'
Dump after common sequence discovery.
`-fdump-rtl-shorten'
Dump after shortening branches.
`-fdump-rtl-sibling'
Dump after sibling call optimizations.
`-fdump-rtl-split1'
`-fdump-rtl-split2'
`-fdump-rtl-split3'
`-fdump-rtl-split4'
`-fdump-rtl-split5'
`-fdump-rtl-split1', `-fdump-rtl-split2',
`-fdump-rtl-split3', `-fdump-rtl-split4' and
`-fdump-rtl-split5' enable dumping after five rounds of
instruction splitting.
`-fdump-rtl-sms'
Dump after modulo scheduling. This pass is only run on some
architectures.
`-fdump-rtl-stack'
Dump after conversion from GCC's "flat register file"
registers to the x87's stack-like registers. This pass is
only run on x86 variants.
`-fdump-rtl-subreg1'
`-fdump-rtl-subreg2'
`-fdump-rtl-subreg1' and `-fdump-rtl-subreg2' enable dumping
after the two subreg expansion passes.
`-fdump-rtl-unshare'
Dump after all rtl has been unshared.
`-fdump-rtl-vartrack'
Dump after variable tracking.
`-fdump-rtl-vregs'
Dump after converting virtual registers to hard registers.
`-fdump-rtl-web'
Dump after live range splitting.
`-fdump-rtl-regclass'
`-fdump-rtl-subregs_of_mode_init'
`-fdump-rtl-subregs_of_mode_finish'
`-fdump-rtl-dfinit'
`-fdump-rtl-dfinish'
These dumps are defined but always produce empty files.
`-fdump-rtl-all'
Produce all the dumps listed above.
`-dA'
Annotate the assembler output with miscellaneous debugging
information.
`-dD'
Dump all macro definitions, at the end of preprocessing, in
addition to normal output.
`-dH'
Produce a core dump whenever an error occurs.
`-dm'
Print statistics on memory usage, at the end of the run, to
standard error.
`-dp'
Annotate the assembler output with a comment indicating which
pattern and alternative was used. The length of each
instruction is also printed.
`-dP'
Dump the RTL in the assembler output as a comment before each
instruction. Also turns on `-dp' annotation.
`-dv'
For each of the other indicated dump files
(`-fdump-rtl-PASS'), dump a representation of the control
flow graph suitable for viewing with VCG to `FILE.PASS.vcg'.
`-dx'
Just generate RTL for a function instead of compiling it.
Usually used with `-fdump-rtl-expand'.
`-dy'
Dump debugging information during parsing, to standard error.
`-fdump-noaddr'
When doing debugging dumps, suppress address output. This makes
it more feasible to use diff on debugging dumps for compiler
invocations with different compiler binaries and/or different text
/ bss / data / heap / stack / dso start locations.
`-fdump-unnumbered'
When doing debugging dumps, suppress instruction numbers and
address output. This makes it more feasible to use diff on
debugging dumps for compiler invocations with different options,
in particular with and without `-g'.
`-fdump-unnumbered-links'
When doing debugging dumps (see `-d' option above), suppress
instruction numbers for the links to the previous and next
instructions in a sequence.
`-fdump-translation-unit (C++ only)'
`-fdump-translation-unit-OPTIONS (C++ only)'
Dump a representation of the tree structure for the entire
translation unit to a file. The file name is made by appending
`.tu' to the source file name. If the `-OPTIONS' form is used,
OPTIONS controls the details of the dump as described for the
`-fdump-tree' options.
`-fdump-class-hierarchy (C++ only)'
`-fdump-class-hierarchy-OPTIONS (C++ only)'
Dump a representation of each class's hierarchy and virtual
function table layout to a file. The file name is made by
appending `.class' to the source file name. If the `-OPTIONS'
form is used, OPTIONS controls the details of the dump as
described for the `-fdump-tree' options.
`-fdump-ipa-SWITCH'
Control the dumping at various stages of inter-procedural analysis
language tree to a file. The file name is generated by appending
a switch specific suffix to the source file name. The following
dumps are possible:
`all'
Enables all inter-procedural analysis dumps.
`cgraph'
Dumps information about call-graph optimization, unused
function removal, and inlining decisions.
`inline'
Dump after function inlining.
`-fdump-statistics-OPTION'
Enable and control dumping of pass statistics in a separate file.
The file name is generated by appending a suffix ending in
`.statistics' to the source file name. If the `-OPTION' form is
used, `-stats' will cause counters to be summed over the whole
compilation unit while `-details' will dump every event as the
passes generate them. The default with no option is to sum
counters for each function compiled.
`-fdump-tree-SWITCH'
`-fdump-tree-SWITCH-OPTIONS'
Control the dumping at various stages of processing the
intermediate language tree to a file. The file name is generated
by appending a switch specific suffix to the source file name. If
the `-OPTIONS' form is used, OPTIONS is a list of `-' separated
options that control the details of the dump. Not all options are
applicable to all dumps, those which are not meaningful will be
ignored. The following options are available
`address'
Print the address of each node. Usually this is not
meaningful as it changes according to the environment and
source file. Its primary use is for tying up a dump file
with a debug environment.
`slim'
Inhibit dumping of members of a scope or body of a function
merely because that scope has been reached. Only dump such
items when they are directly reachable by some other path.
When dumping pretty-printed trees, this option inhibits
dumping the bodies of control structures.
`raw'
Print a raw representation of the tree. By default, trees are
pretty-printed into a C-like representation.
`details'
Enable more detailed dumps (not honored by every dump option).
`stats'
Enable dumping various statistics about the pass (not honored
by every dump option).
`blocks'
Enable showing basic block boundaries (disabled in raw dumps).
`vops'
Enable showing virtual operands for every statement.
`lineno'
Enable showing line numbers for statements.
`uid'
Enable showing the unique ID (`DECL_UID') for each variable.
`verbose'
Enable showing the tree dump for each statement.
`all'
Turn on all options, except `raw', `slim', `verbose' and
`lineno'.
The following tree dumps are possible:
`original'
Dump before any tree based optimization, to `FILE.original'.
`optimized'
Dump after all tree based optimization, to `FILE.optimized'.
`gimple'
Dump each function before and after the gimplification pass
to a file. The file name is made by appending `.gimple' to
the source file name.
`cfg'
Dump the control flow graph of each function to a file. The
file name is made by appending `.cfg' to the source file name.
`vcg'
Dump the control flow graph of each function to a file in VCG
format. The file name is made by appending `.vcg' to the
source file name. Note that if the file contains more than
one function, the generated file cannot be used directly by
VCG. You will need to cut and paste each function's graph
into its own separate file first.
`ch'
Dump each function after copying loop headers. The file name
is made by appending `.ch' to the source file name.
`ssa'
Dump SSA related information to a file. The file name is
made by appending `.ssa' to the source file name.
`alias'
Dump aliasing information for each function. The file name
is made by appending `.alias' to the source file name.
`ccp'
Dump each function after CCP. The file name is made by
appending `.ccp' to the source file name.
`storeccp'
Dump each function after STORE-CCP. The file name is made by
appending `.storeccp' to the source file name.
`pre'
Dump trees after partial redundancy elimination. The file
name is made by appending `.pre' to the source file name.
`fre'
Dump trees after full redundancy elimination. The file name
is made by appending `.fre' to the source file name.
`copyprop'
Dump trees after copy propagation. The file name is made by
appending `.copyprop' to the source file name.
`store_copyprop'
Dump trees after store copy-propagation. The file name is
made by appending `.store_copyprop' to the source file name.
`dce'
Dump each function after dead code elimination. The file
name is made by appending `.dce' to the source file name.
`mudflap'
Dump each function after adding mudflap instrumentation. The
file name is made by appending `.mudflap' to the source file
name.
`sra'
Dump each function after performing scalar replacement of
aggregates. The file name is made by appending `.sra' to the
source file name.
`sink'
Dump each function after performing code sinking. The file
name is made by appending `.sink' to the source file name.
`dom'
Dump each function after applying dominator tree
optimizations. The file name is made by appending `.dom' to
the source file name.
`dse'
Dump each function after applying dead store elimination.
The file name is made by appending `.dse' to the source file
name.
`phiopt'
Dump each function after optimizing PHI nodes into
straightline code. The file name is made by appending
`.phiopt' to the source file name.
`forwprop'
Dump each function after forward propagating single use
variables. The file name is made by appending `.forwprop' to
the source file name.
`copyrename'
Dump each function after applying the copy rename
optimization. The file name is made by appending
`.copyrename' to the source file name.
`nrv'
Dump each function after applying the named return value
optimization on generic trees. The file name is made by
appending `.nrv' to the source file name.
`vect'
Dump each function after applying vectorization of loops.
The file name is made by appending `.vect' to the source file
name.
`vrp'
Dump each function after Value Range Propagation (VRP). The
file name is made by appending `.vrp' to the source file name.
`all'
Enable all the available tree dumps with the flags provided
in this option.
`-ftree-vectorizer-verbose=N'
This option controls the amount of debugging output the vectorizer
prints. This information is written to standard error, unless
`-fdump-tree-all' or `-fdump-tree-vect' is specified, in which
case it is output to the usual dump listing file, `.vect'. For
N=0 no diagnostic information is reported. If N=1 the vectorizer
reports each loop that got vectorized, and the total number of
loops that got vectorized. If N=2 the vectorizer also reports
non-vectorized loops that passed the first analysis phase
(vect_analyze_loop_form) - i.e. countable, inner-most, single-bb,
single-entry/exit loops. This is the same verbosity level that
`-fdump-tree-vect-stats' uses. Higher verbosity levels mean
either more information dumped for each reported loop, or same
amount of information reported for more loops: If N=3, alignment
related information is added to the reports. If N=4,
data-references related information (e.g. memory dependences,
memory access-patterns) is added to the reports. If N=5, the
vectorizer reports also non-vectorized inner-most loops that did
not pass the first analysis phase (i.e., may not be countable, or
may have complicated control-flow). If N=6, the vectorizer
reports also non-vectorized nested loops. For N=7, all the
information the vectorizer generates during its analysis and
transformation is reported. This is the same verbosity level that
`-fdump-tree-vect-details' uses.
`-frandom-seed=STRING'
This option provides a seed that GCC uses when it would otherwise
use random numbers. It is used to generate certain symbol names
that have to be different in every compiled file. It is also used
to place unique stamps in coverage data files and the object files
that produce them. You can use the `-frandom-seed' option to
produce reproducibly identical object files.
The STRING should be different for every file you compile.
`-fsched-verbose=N'
On targets that use instruction scheduling, this option controls
the amount of debugging output the scheduler prints. This
information is written to standard error, unless
`-fdump-rtl-sched1' or `-fdump-rtl-sched2' is specified, in which
case it is output to the usual dump listing file, `.sched' or
`.sched2' respectively. However for N greater than nine, the
output is always printed to standard error.
For N greater than zero, `-fsched-verbose' outputs the same
information as `-fdump-rtl-sched1' and `-fdump-rtl-sched2'. For N
greater than one, it also output basic block probabilities,
detailed ready list information and unit/insn info. For N greater
than two, it includes RTL at abort point, control-flow and regions
info. And for N over four, `-fsched-verbose' also includes
dependence info.
`-save-temps'
Store the usual "temporary" intermediate files permanently; place
them in the current directory and name them based on the source
file. Thus, compiling `foo.c' with `-c -save-temps' would produce
files `foo.i' and `foo.s', as well as `foo.o'. This creates a
preprocessed `foo.i' output file even though the compiler now
normally uses an integrated preprocessor.
When used in combination with the `-x' command line option,
`-save-temps' is sensible enough to avoid over writing an input
source file with the same extension as an intermediate file. The
corresponding intermediate file may be obtained by renaming the
source file before using `-save-temps'.
`-time[=FILE]'
Report the CPU time taken by each subprocess in the compilation
sequence. For C source files, this is the compiler proper and
assembler (plus the linker if linking is done).
Without the specification of an output file, the output looks like
this:
# cc1 0.12 0.01
# as 0.00 0.01
The first number on each line is the "user time", that is time
spent executing the program itself. The second number is "system
time", time spent executing operating system routines on behalf of
the program. Both numbers are in seconds.
With the specification of an output file, the output is appended
to the named file, and it looks like this:
0.12 0.01 cc1 OPTIONS
0.00 0.01 as OPTIONS
The "user time" and the "system time" are moved before the program
name, and the options passed to the program are displayed, so that
one can later tell what file was being compiled, and with which
options.
`-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.
It can be enabled even if var-tracking is disabled, in which case
annotations will be created and maintained, but discarded at the
end.
`-fvar-tracking-assignments-toggle'
Toggle `-fvar-tracking-assignments', in the same way that
`-gtoggle' toggles `-g'.
`-print-file-name=LIBRARY'
Print the full absolute name of the library file LIBRARY that
would be used when linking--and don't do anything else. With this
option, GCC does not compile or link anything; it just prints the
file name.
`-print-multi-directory'
Print the directory name corresponding to the multilib selected by
any other switches present in the command line. This directory is
supposed to exist in `GCC_EXEC_PREFIX'.
`-print-multi-lib'
Print the mapping from multilib directory names to compiler
switches that enable them. The directory name is separated from
the switches by `;', and each switch starts with an `@' instead of
the `-', without spaces between multiple switches. This is
supposed to ease shell-processing.
`-print-multi-os-directory'
Print the path to OS libraries for the selected multilib, relative
to some `lib' subdirectory. If OS libraries are present in the
`lib' subdirectory and no multilibs are used, this is usually just
`.', if OS libraries are present in `libSUFFIX' sibling
directories this prints e.g. `../lib64', `../lib' or `../lib32',
or if OS libraries are present in `lib/SUBDIR' subdirectories it
prints e.g. `amd64', `sparcv9' or `ev6'.
`-print-prog-name=PROGRAM'
Like `-print-file-name', but searches for a program such as `cpp'.
`-print-libgcc-file-name'
Same as `-print-file-name=libgcc.a'.
This is useful when you use `-nostdlib' or `-nodefaultlibs' but
you do want to link with `libgcc.a'. You can do
gcc -nostdlib FILES... `gcc -print-libgcc-file-name`
`-print-search-dirs'
Print the name of the configured installation directory and a list
of program and library directories `gcc' will search--and don't do
anything else.
This is useful when `gcc' prints the error message `installation
problem, cannot exec cpp0: No such file or directory'. To resolve
this you either need to put `cpp0' and the other compiler
components where `gcc' expects to find them, or you can set the
environment variable `GCC_EXEC_PREFIX' to the directory where you
installed them. Don't forget the trailing `/'. Environment
Variables.
`-print-sysroot'
Print the target sysroot directory that will be used during
compilation. This is the target sysroot specified either at
configure time or using the `--sysroot' option, possibly with an
extra suffix that depends on compilation options. If no target
sysroot is specified, the option prints nothing.
`-print-sysroot-headers-suffix'
Print the suffix added to the target sysroot when searching for
headers, or give an error if the compiler is not configured with
such a suffix--and don't do anything else.
`-dumpmachine'
Print the compiler's target machine (for example,
`i686-pc-linux-gnu')--and don't do anything else.
`-dumpversion'
Print the compiler version (for example, `3.0')--and don't do
anything else.
`-dumpspecs'
Print the compiler's built-in specs--and don't do anything else.
(This is used when GCC itself is being built.) Spec Files.
`-feliminate-unused-debug-types'
Normally, when producing DWARF2 output, GCC will emit debugging
information for all types declared in a compilation unit,
regardless of whether or not they are actually used in that
compilation unit. Sometimes this is useful, such as 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. With this
option, GCC will avoid producing debug symbol output for types
that are nowhere used in the source file being compiled.
Info Catalog
(gcc.info.gz) Warning Options
(gcc.info.gz) Invoking GCC
(gcc.info.gz) Optimize Options
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