@item C Language Options
@xref{C Dialect Options,,Options Controlling C Dialect}.
@gccoptlist{-ansi -std=@var{standard} -fgnu89-inline @gol
+-fpermitted-flt-eval-methods=@var{standard} @gol
-aux-info @var{filename} -fallow-parameterless-variadic-functions @gol
-fno-asm -fno-builtin -fno-builtin-@var{function} -fgimple@gol
-fhosted -ffreestanding -fopenacc -fopenmp -fopenmp-simd @gol
@gccoptlist{-fsyntax-only -fmax-errors=@var{n} -Wpedantic @gol
-pedantic-errors @gol
-w -Wextra -Wall -Waddress -Waggregate-return @gol
+-Walloc-zero -Walloc-size-larger-than=@var{n}
-Walloca -Walloca-larger-than=@var{n} @gol
-Wno-aggressive-loop-optimizations -Warray-bounds -Warray-bounds=@var{n} @gol
-Wno-attributes -Wbool-compare -Wbool-operation @gol
+-Wno-builtin-declaration-mismatch @gol
-Wno-builtin-macro-redefined -Wc90-c99-compat -Wc99-c11-compat @gol
-Wc++-compat -Wc++11-compat -Wc++14-compat -Wcast-align -Wcast-qual @gol
-Wchar-subscripts -Wclobbered -Wcomment -Wconditionally-supported @gol
-Wsizeof-pointer-memaccess -Wsizeof-array-argument @gol
-Wstack-protector -Wstack-usage=@var{len} -Wstrict-aliasing @gol
-Wstrict-aliasing=n -Wstrict-overflow -Wstrict-overflow=@var{n} @gol
+-Wstringop-overflow=@var{n} @gol
-Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{]} @gol
-Wsuggest-final-types @gol -Wsuggest-final-methods -Wsuggest-override @gol
-Wmissing-format-attribute -Wsubobject-linkage @gol
-fno-ira-share-spill-slots @gol
-fisolate-erroneous-paths-dereference -fisolate-erroneous-paths-attribute @gol
-fivopts -fkeep-inline-functions -fkeep-static-functions @gol
--fkeep-static-consts -flive-range-shrinkage @gol
+-fkeep-static-consts -flimit-function-alignment -flive-range-shrinkage @gol
-floop-block -floop-interchange -floop-strip-mine @gol
-floop-unroll-and-jam -floop-nest-optimize @gol
-floop-parallelize-all -flra-remat -flto -flto-compression-level @gol
-fmove-loop-invariants -fno-branch-count-reg @gol
-fno-defer-pop -fno-fp-int-builtin-inexact -fno-function-cse @gol
-fno-guess-branch-probability -fno-inline -fno-math-errno -fno-peephole @gol
--fno-peephole2 -fno-sched-interblock -fno-sched-spec -fno-signed-zeros @gol
+-fno-peephole2 -fno-printf-return-value -fno-sched-interblock @gol
+-fno-sched-spec -fno-signed-zeros @gol
-fno-toplevel-reorder -fno-trapping-math -fno-zero-initialized-in-bss @gol
-fomit-frame-pointer -foptimize-sibling-calls @gol
-fpartial-inlining -fpeel-loops -fpredictive-commoning @gol
--fprefetch-loop-arrays -fprintf-return-value @gol
+-fprefetch-loop-arrays @gol
-fprofile-correction @gol
-fprofile-use -fprofile-use=@var{path} -fprofile-values @gol
-fprofile-reorder-functions @gol
-ftree-builtin-call-dce -ftree-ccp -ftree-ch @gol
-ftree-coalesce-vars -ftree-copy-prop -ftree-dce -ftree-dominator-opts @gol
-ftree-dse -ftree-forwprop -ftree-fre -fcode-hoisting -ftree-loop-if-convert @gol
--ftree-loop-if-convert-stores -ftree-loop-im @gol
+-ftree-loop-im @gol
-ftree-phiprop -ftree-loop-distribution -ftree-loop-distribute-patterns @gol
-ftree-loop-ivcanon -ftree-loop-linear -ftree-loop-optimize @gol
-ftree-loop-vectorize @gol
-mcrc -mdsp-packa -mdvbf -mlock -mmac-d16 -mmac-24 -mrtsc -mswape @gol
-mtelephony -mxy -misize -mannotate-align -marclinux -marclinux_prof @gol
-mlong-calls -mmedium-calls -msdata @gol
--mucb-mcount -mvolatile-cache -mtp-regno=@var{regno} @gol
+-mvolatile-cache -mtp-regno=@var{regno} @gol
-malign-call -mauto-modify-reg -mbbit-peephole -mno-brcc @gol
-mcase-vector-pcrel -mcompact-casesi -mno-cond-exec -mearly-cbranchsi @gol
-mexpand-adddi -mindexed-loads -mlra -mlra-priority-none @gol
@gccoptlist{-mapcs-frame -mno-apcs-frame @gol
-mabi=@var{name} @gol
-mapcs-stack-check -mno-apcs-stack-check @gol
--mapcs-float -mno-apcs-float @gol
-mapcs-reentrant -mno-apcs-reentrant @gol
-msched-prolog -mno-sched-prolog @gol
-mlittle-endian -mbig-endian @gol
-mslow-flash-data @gol
-masm-syntax-unified @gol
-mrestrict-it @gol
--mpure-code}
+-mpure-code @gol
+-mcmse}
@emph{AVR Options}
@gccoptlist{-mmcu=@var{mcu} -mabsdata -maccumulate-args @gol
@emph{HPPA Options}
@gccoptlist{-march=@var{architecture-type} @gol
--mdisable-fpregs -mdisable-indexing @gol
+-mcaller-copies -mdisable-fpregs -mdisable-indexing @gol
-mfast-indirect-calls -mgas -mgnu-ld -mhp-ld @gol
-mfixed-range=@var{register-range} @gol
-mjump-in-delay -mlinker-opt -mlong-calls @gol
in effect for @code{inline} functions. @xref{Common Predefined
Macros,,,cpp,The C Preprocessor}.
+@item -fpermitted-flt-eval-methods=@var{style}
+@opindex fpermitted-flt-eval-methods
+@opindex fpermitted-flt-eval-methods=c11
+@opindex fpermitted-flt-eval-methods=ts-18661-3
+ISO/IEC TS 18661-3 defines new permissible values for
+@code{FLT_EVAL_METHOD} that indicate that operations and constants with
+a semantic type that is an interchange or extended format should be
+evaluated to the precision and range of that type. These new values are
+a superset of those permitted under C99/C11, which does not specify the
+meaning of other positive values of @code{FLT_EVAL_METHOD}. As such, code
+conforming to C11 may not have been written expecting the possibility of
+the new values.
+
+@option{-fpermitted-flt-eval-methods} specifies whether the compiler
+should allow only the values of @code{FLT_EVAL_METHOD} specified in C99/C11,
+or the extended set of values specified in ISO/IEC TS 18661-3.
+
+@var{style} is either @code{c11} or @code{ts-18661-3} as appropriate.
+
+The default when in a standards compliant mode (@option{-std=c11} or similar)
+is @option{-fpermitted-flt-eval-methods=c11}. The default when in a GNU
+dialect (@option{-std=gnu11} or similar) is
+@option{-fpermitted-flt-eval-methods=ts-18661-3}.
+
@item -aux-info @var{filename}
@opindex aux-info
Output to the given filename prototyped declarations for all functions
false positives.
@end table
+@item -Wstringop-overflow
+@itemx -Wstringop-overflow=@var{type}
+@opindex Wstringop-overflow
+@opindex Wno-stringop-overflow
+Warn for calls to string manipulation functions such as @code{memcpy} and
+@code{strcpy} that are determined to overflow the destination buffer. The
+optional argument is one greater than the type of Object Size Checking to
+perform to determine the size of the destination. @xref{Object Size Checking}.
+The argument is meaningful only for functions that operate on character arrays
+but not for raw memory functions like @code{memcpy} which always make use
+of Object Size type-0. The option also warns for calls that specify a size
+in excess of the largest possible object or at most @code{SIZE_MAX / 2} bytes.
+The option produces the best results with optimization enabled but can detect
+a small subset of simple buffer overflows even without optimization in
+calls to the GCC built-in functions like @code{__builtin_memcpy} that
+correspond to the standard functions. In any case, the option warns about
+just a subset of buffer overflows detected by the corresponding overflow
+checking built-ins. For example, the option will issue a warning for
+the @code{strcpy} call below because it copies at least 5 characters
+(the string @code{"blue"} including the terminating NUL) into the buffer
+of size 4.
+
+@smallexample
+enum Color @{ blue, purple, yellow @};
+const char* f (enum Color clr)
+@{
+ static char buf [4];
+ const char *str;
+ switch (clr)
+ @{
+ case blue: str = "blue"; break;
+ case purple: str = "purple"; break;
+ case yellow: str = "yellow"; break;
+ @}
+
+ return strcpy (buf, str); // warning here
+@}
+@end smallexample
+
+Option @option{-Wstringop-overflow=2} is enabled by default.
+
+@table @gcctabopt
+@item -Wstringop-overflow
+@item -Wstringop-overflow=1
+@opindex Wstringop-overflow
+@opindex Wno-stringop-overflow
+The @option{-Wstringop-overflow=1} option uses type-zero Object Size Checking
+to determine the sizes of destination objects. This is the default setting
+of the option. At this setting the option will not warn for writes past
+the end of subobjects of larger objects accessed by pointers unless the
+size of the largest surrounding object is known. When the destination may
+be one of several objects it is assumed to be the largest one of them. On
+Linux systems, when optimization is enabled at this setting the option warns
+for the same code as when the @code{_FORTIFY_SOURCE} macro is defined to
+a non-zero value.
+
+@item -Wstringop-overflow=2
+The @option{-Wstringop-overflow=2} option uses type-one Object Size Checking
+to determine the sizes of destination objects. At this setting the option
+will warn about overflows when writing to members of the largest complete
+objects whose exact size is known. It will, however, not warn for excessive
+writes to the same members of unknown objects referenced by pointers since
+they may point to arrays containing unknown numbers of elements.
+
+@item -Wstringop-overflow=3
+The @option{-Wstringop-overflow=3} option uses type-two Object Size Checking
+to determine the sizes of destination objects. At this setting the option
+warns about overflowing the smallest object or data member. This is the
+most restrictive setting of the option that may result in warnings for safe
+code.
+
+@item -Wstringop-overflow=4
+The @option{-Wstringop-overflow=4} option uses type-three Object Size Checking
+to determine the sizes of destination objects. At this setting the option
+will warn about overflowing any data members, and when the destination is
+one of several objects it uses the size of the largest of them to decide
+whether to issue a warning. Similarly to @option{-Wstringop-overflow=3} this
+setting of the option may result in warnings for benign code.
+@end table
+
@item -Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{]}
@opindex Wsuggest-attribute=
@opindex Wno-suggest-attribute=
Warn about overriding virtual functions that are not marked with the override
keyword.
+@item -Walloc-zero
+@opindex Wno-alloc-zero
+@opindex Walloc-zero
+Warn about calls to allocation functions decorated with attribute
+@code{alloc_size} that specify zero bytes, including those to the built-in
+forms of the functions @code{aligned_alloc}, @code{alloca}, @code{calloc},
+@code{malloc}, and @code{realloc}. Because the behavior of these functions
+when called with a zero size differs among implementations (and in the case
+of @code{realloc} has been deprecated) relying on it may result in subtle
+portability bugs and should be avoided.
+
+@item -Walloc-size-larger-than=@var{n}
+Warn about calls to functions decorated with attribute @code{alloc_size}
+that attempt to allocate objects larger than the specified number of bytes,
+or where the result of the size computation in an integer type with infinite
+precision would exceed @code{SIZE_MAX / 2}. The option argument @var{n}
+may end in one of the standard suffixes designating a multiple of bytes
+such as @code{kB} and @code{KiB} for kilobyte and kibibyte, respectively,
+@code{MB} and @code{MiB} for magabyte and mebibyte, and so on.
+@xref{Function Attributes}.
+
@item -Walloca
@opindex Wno-alloca
@opindex Walloca
construct, known from C++, was introduced with ISO C99 and is by default
allowed in GCC@. It is not supported by ISO C90. @xref{Mixed Declarations}.
+@item -Wexpansion-to-defined
+@opindex Wexpansion-to-defined
+Warn whenever @samp{defined} is encountered in the expansion of a macro.
+This warning is also enabled by @option{-Wpedantic} and @option{-Wextra}.
+
@item -Wundef
@opindex Wundef
@opindex Wno-undef
etc. This does not stop errors for incorrect use of supported
attributes.
+@item -Wno-builtin-declaration-mismatch
+@opindex Wno-builtin-declaration-mismatch
+@opindex Wbuiltin-declaration-mismatch
+Warn if a built-in function is declared with the wrong signature.
+This warning is enabled by default.
+
@item -Wno-builtin-macro-redefined
@opindex Wno-builtin-macro-redefined
@opindex Wbuiltin-macro-redefined
@opindex fno-keep-inline-dllexport
This is a more fine-grained version of @option{-fkeep-inline-functions},
which applies only to functions that are declared using the @code{dllexport}
-attribute or declspec (@xref{Function Attributes,,Declaring Attributes of
-Functions}.)
+attribute or declspec. @xref{Function Attributes,,Declaring Attributes of
+Functions}.
@item -fkeep-inline-functions
@opindex fkeep-inline-functions
vectorization pass to handle these loops. This is enabled by default
if vectorization is enabled.
-@item -ftree-loop-if-convert-stores
-@opindex ftree-loop-if-convert-stores
-Attempt to also if-convert conditional jumps containing memory writes.
-This transformation can be unsafe for multi-threaded programs as it
-transforms conditional memory writes into unconditional memory writes.
-For example,
-@smallexample
-for (i = 0; i < N; i++)
- if (cond)
- A[i] = expr;
-@end smallexample
-is transformed to
-@smallexample
-for (i = 0; i < N; i++)
- A[i] = cond ? expr : A[i];
-@end smallexample
-potentially producing data races.
-
@item -ftree-loop-distribution
@opindex ftree-loop-distribution
Perform loop distribution. This flag can improve cache performance on
Disabled at level @option{-Os}.
-@item -fprintf-return-value
-@opindex fprintf-return-value
-Substitute constants for known return value of formatted output functions
-such as @code{sprintf}, @code{snprintf}, @code{vsprintf}, and @code{vsnprintf}
-(but not @code{printf} of @code{fprintf}). This transformation allows GCC
-to optimize or even eliminate branches based on the known return value of
-these functions called with arguments that are either constant, or whose
-values are known to be in a range that makes determining the exact return
-value possible. For example, both the branch and the body of the @code{if}
-statement (but not the call to @code{snprint}) can be optimized away when
-@code{i} is a 32-bit or smaller integer because the return value is guaranteed
-to be at most 8.
+@item -fno-printf-return-value
+@opindex fno-printf-return-value
+Do not substitute constants for known return value of formatted output
+functions such as @code{sprintf}, @code{snprintf}, @code{vsprintf}, and
+@code{vsnprintf} (but not @code{printf} of @code{fprintf}). This
+transformation allows GCC to optimize or even eliminate branches based
+on the known return value of these functions called with arguments that
+are either constant, or whose values are known to be in a range that
+makes determining the exact return value possible. For example, when
+@option{-fprintf-return-value} is in effect, both the branch and the
+body of the @code{if} statement (but not the call to @code{snprint})
+can be optimized away when @code{i} is a 32-bit or smaller integer
+because the return value is guaranteed to be at most 8.
@smallexample
char buf[9];
The @option{-fprintf-return-value} option relies on other optimizations
and yields best results with @option{-O2}. It works in tandem with the
@option{-Wformat-length} option. The @option{-fprintf-return-value}
-option is disabled by default.
+option is enabled by default.
@item -fno-peephole
@itemx -fno-peephole2
Enabled at levels @option{-O2}, @option{-O3}.
+@item -flimit-function-alignment
+If this option is enabled, the compiler tries to avoid unnecessarily
+overaligning functions. It attempts to instruct the assembler to align
+by the amount specified by @option{-falign-functions}, but not to
+skip more bytes than the size of the function.
+
@item -falign-labels
@itemx -falign-labels=@var{n}
@opindex falign-labels
@option{-ftree-vectorize}, and @option{ftree-loop-distribute-patterns}.
Before you can use this option, you must first generate profiling information.
-@xref{Optimize Options}, for information about the @option{-fprofile-generate}
-option.
+@xref{Instrumentation Options}, for information about the
+@option{-fprofile-generate} option.
By default, GCC emits an error message if the feedback profiles do not
match the source code. This error can be turned into a warning by using
@item -fexcess-precision=@var{style}
@opindex fexcess-precision
This option allows further control over excess precision on machines
-where floating-point registers have more precision than the IEEE
-@code{float} and @code{double} types and the processor does not
-support operations rounding to those types. By default,
-@option{-fexcess-precision=fast} is in effect; this means that
-operations are carried out in the precision of the registers and that
-it is unpredictable when rounding to the types specified in the source
-code takes place. When compiling C, if
-@option{-fexcess-precision=standard} is specified then excess
-precision follows the rules specified in ISO C99; in particular,
+where floating-point operations occur in a format with more precision or
+range than the IEEE standard and interchange floating-point types. By
+default, @option{-fexcess-precision=fast} is in effect; this means that
+operations may be carried out in a wider precision than the types specified
+in the source if that would result in faster code, and it is unpredictable
+when rounding to the types specified in the source code takes place.
+When compiling C, if @option{-fexcess-precision=standard} is specified then
+excess precision follows the rules specified in ISO C99; in particular,
both casts and assignments cause values to be rounded to their
semantic types (whereas @option{-ffloat-store} only affects
assignments). This option is enabled by default for C if a strict
@item -fsanitize=kernel-address
@opindex fsanitize=kernel-address
Enable AddressSanitizer for Linux kernel.
-The option enables @option{-fsanitize-address-use-after-scope}.
See @uref{https://github.com/google/kasan/wiki} for more details.
@item -fsanitize=thread
@opindex fbounds-check
For front ends that support it, generate additional code to check that
indices used to access arrays are within the declared range. This is
-currently only supported by the Fortran front end, where
-this option defaults to true and false respectively.
+currently only supported by the Fortran front end, where this option
+defaults to false.
@item -fcheck-pointer-bounds
@opindex fcheck-pointer-bounds
performance of the code. Permissible values for this option are:
@samp{generic}, @samp{cortex-a35}, @samp{cortex-a53}, @samp{cortex-a57},
@samp{cortex-a72}, @samp{cortex-a73}, @samp{exynos-m1}, @samp{falkor},
-@samp{qdf24xx}, @samp{thunderx}, @samp{xgene1}, @samp{vulcan},
-@samp{cortex-a57.cortex-a53}, @samp{cortex-a72.cortex-a53},
+@samp{qdf24xx}, @samp{xgene1}, @samp{vulcan}, @samp{thunderx},
+@samp{thunderxt88}, @samp{thunderxt88p1}, @samp{thunderxt81},
+@samp{thunderxt83}, @samp{cortex-a57.cortex-a53}, @samp{cortex-a72.cortex-a53},
@samp{cortex-a73.cortex-a35}, @samp{cortex-a73.cortex-a53}, @samp{native}.
The values @samp{cortex-a57.cortex-a53}, @samp{cortex-a72.cortex-a53},
built for @w{@code{arc-linux-uclibc}} and @w{@code{arceb-linux-uclibc}}
targets.
-@item -mucb-mcount
-@opindex mucb-mcount
-Instrument with mcount calls as used in UCB code. I.e. do the
-counting in the callee, not the caller. By default ARC instrumentation
-counts in the caller.
-
@item -mvolatile-cache
@opindex mvolatile-cache
Use ordinarily cached memory accesses for volatile references. This is the
system is required to provide these functions. The default is
@option{-mno-apcs-stack-check}, since this produces smaller code.
-@c not currently implemented
-@item -mapcs-float
-@opindex mapcs-float
-Pass floating-point arguments using the floating-point registers. This is
-one of the variants of the APCS@. This option is recommended if the
-target hardware has a floating-point unit or if a lot of floating-point
-arithmetic is going to be performed by the code. The default is
-@option{-mno-apcs-float}, since the size of integer-only code is
-slightly increased if @option{-mapcs-float} is used.
-
@c not currently implemented
@item -mapcs-reentrant
@opindex mapcs-reentrant
@item -mfpu=@var{name}
@opindex mfpu
This specifies what floating-point hardware (or hardware emulation) is
-available on the target. Permissible names are: @samp{vfp}, @samp{vfpv3},
+available on the target. Permissible names are: @samp{vfpv2}, @samp{vfpv3},
@samp{vfpv3-fp16}, @samp{vfpv3-d16}, @samp{vfpv3-d16-fp16}, @samp{vfpv3xd},
-@samp{vfpv3xd-fp16}, @samp{neon}, @samp{neon-fp16}, @samp{vfpv4},
+@samp{vfpv3xd-fp16}, @samp{neon-vfpv3}, @samp{neon-fp16}, @samp{vfpv4},
@samp{vfpv4-d16}, @samp{fpv4-sp-d16}, @samp{neon-vfpv4},
@samp{fpv5-d16}, @samp{fpv5-sp-d16},
@samp{fp-armv8}, @samp{neon-fp-armv8} and @samp{crypto-neon-fp-armv8}.
+Note that @samp{neon} is an alias for @samp{neon-vfpv3} and @samp{vfp}
+is an alias for @samp{vfpv2}.
If @option{-msoft-float} is specified this specifies the format of
floating-point values.
ELF processor-specific section attribute @code{SHF_ARM_PURECODE}. This option
is only available when generating non-pic code for ARMv7-M targets.
+@item -mcmse
+@opindex mcmse
+Generate secure code as per the "ARMv8-M Security Extensions: Requirements on
+Development Tools Engineering Specification", which can be found on
+@url{http://infocenter.arm.com/help/topic/com.arm.doc.ecm0359818/ECM0359818_armv8m_security_extensions_reqs_on_dev_tools_1_0.pdf}.
@end table
@node AVR Options
Assume that all data in static storage can be accessed by LDS / STS
instructions. This option has only an effect on reduced Tiny devices like
-ATtiny40.
+ATtiny40. See also the @code{absdata}
+@ref{AVR Variable Attributes,variable attribute}.
@item -maccumulate-args
@opindex maccumulate-args
@opindex mpa-risc-2-0
Synonyms for @option{-march=1.0}, @option{-march=1.1}, and @option{-march=2.0} respectively.
+@item -mcaller-copies
+@opindex mcaller-copies
+The caller copies function arguments passed by hidden reference. This
+option should be used with care as it is not compatible with the default
+32-bit runtime. However, only aggregates larger than eight bytes are
+passed by hidden reference and the option provides better compatibility
+with OpenMP.
+
@item -mjump-in-delay
@opindex mjump-in-delay
This option is ignored and provided for compatibility purposes only.
Apply partitioned execution optimizations. This is the default when any
level of optimization is selected.
+@item -msoft-stack
+@opindex msoft-stack
+Generate code that does not use @code{.local} memory
+directly for stack storage. Instead, a per-warp stack pointer is
+maintained explicitly. This enables variable-length stack allocation (with
+variable-length arrays or @code{alloca}), and when global memory is used for
+underlying storage, makes it possible to access automatic variables from other
+threads, or with atomic instructions. This code generation variant is used
+for OpenMP offloading, but the option is exposed on its own for the purpose
+of testing the compiler; to generate code suitable for linking into programs
+using OpenMP offloading, use option @option{-mgomp}.
+
+@item -muniform-simt
+@opindex muniform-simt
+Switch to code generation variant that allows to execute all threads in each
+warp, while maintaining memory state and side effects as if only one thread
+in each warp was active outside of OpenMP SIMD regions. All atomic operations
+and calls to runtime (malloc, free, vprintf) are conditionally executed (iff
+current lane index equals the master lane index), and the register being
+assigned is copied via a shuffle instruction from the master lane. Outside of
+SIMD regions lane 0 is the master; inside, each thread sees itself as the
+master. Shared memory array @code{int __nvptx_uni[]} stores all-zeros or
+all-ones bitmasks for each warp, indicating current mode (0 outside of SIMD
+regions). Each thread can bitwise-and the bitmask at position @code{tid.y}
+with current lane index to compute the master lane index.
+
+@item -mgomp
+@opindex mgomp
+Generate code for use in OpenMP offloading: enables @option{-msoft-stack} and
+@option{-muniform-simt} options, and selects corresponding multilib variant.
+
@end table
@node PDP-11 Options
projects / gcc.git / blobdiff