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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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sparse(1) General Commands Manual sparse(1)
sparse - Semantic Parser for C
sparse [WARNING OPTIONS]... file.c
Sparse parses C source and looks for errors, producing warnings
on standard error.
Sparse accepts options controlling the set of warnings to
generate. To turn on warnings Sparse does not issue by default,
use the corresponding warning option -Wsomething. Sparse issues
some warnings by default; to turn off those warnings, pass the
negation of the associated warning option, -Wno-something.
-fmax-errors=COUNT
Set the maximum number of displayed errors to COUNT, which
should be a numerical value or 'unlimited'. The default
limit is 100.
-fmax-warnings=COUNT
Set the maximum number of displayed warnings to COUNT,
which should be a numerical value or 'unlimited'. The
default limit is 100.
-Wsparse-all
Turn on all sparse warnings, except for those explicitly
disabled via -Wno-something.
-Wsparse-error
Turn all sparse warnings into errors.
-Waddress-space
Warn about code which mixes pointers to different address
spaces.
Sparse allows an extended attribute
__attribute__((address_space(id))) on pointers, which
designates a pointer target in address space id (an
identifier or a constant integer). With -Waddress-space,
Sparse treats pointers with identical target types but
different address spaces as distinct types and will warn
accordingly.
Sparse will also warn on casts which remove the address
space (casts to an integer type or to a plain pointer
type). An exception to this is when the destination type
is uintptr_t (or unsigned long) since such casts are often
used to "get a pointer value representation in an integer
type" and such values are independent of the address
space.
To override these warnings, use a type that includes
__attribute__((force)).
Sparse issues these warnings by default. To turn them
off, use -Wno-address-space.
-Wbitwise
Warn about unsupported operations or type mismatches with
restricted integer types.
Sparse supports an extended attribute,
__attribute__((bitwise)), which creates a new restricted
integer type from a base integer type, distinct from the
base integer type and from any other restricted integer
type not declared in the same declaration or typedef. For
example, this allows programs to create typedefs for
integer types with specific endianness. With -Wbitwise,
Sparse will warn on any use of a restricted type in
arithmetic operations other than bitwise operations, and
on any conversion of one restricted type into another,
except via a cast that includes __attribute__((force)).
__bitwise ends up being a "stronger integer separation",
one that doesn't allow you to mix with non-bitwise
integers, so now it's much harder to lose the type by
mistake.
__bitwise is for *unique types* that cannot be mixed with
other types, and that you'd never want to just use as a
random integer (the integer 0 is special, though, and gets
silently accepted iirc - it's kind of like "NULL" for
pointers). So "gfp_t" or the "safe endianness" types would
be __bitwise: you can only operate on them by doing
specific operations that know about *that* particular
type.
Sparse issues these warnings by default. To turn them
off, use -Wno-bitwise.
-Wbitwise-pointer
Same as -Wbitwise but for casts to or from pointers to
bitwise types.
Sparse does not issue these warnings by default.
-Wcast-from-as
Warn about casts which remove an address space from a
pointer type.
This is similar to -Waddress-space but will also warn on
casts to unsigned long.
Sparse does not issues these warnings by default.
-Wcast-to-as
Warn about casts which add an address space to a pointer
type.
A cast that includes __attribute__((force)) will suppress
this warning. No warning is generated if the original
type is uintptr_t (or unsigned long).
Sparse does not issue these warnings by default.
-Wcast-truncate
Warn about casts that truncate constant values.
Sparse issues these warnings by default. To turn them
off, use -Wno-cast-truncate.
-Wconstant-suffix
Warn if an integer constant is larger than the maximum
representable value of the type indicated by its type
suffix (if any). For example, on a system where ints are
32-bit and longs 64-bit, the constant 0x100000000U is
larger than can be represented by an unsigned int but fits
in an unsigned long. So its type is unsigned long but this
is not indicated by its suffix. In this case, the warning
could be suppressed by using the suffix UL: 0x100000000UL.
Sparse does not issue these warnings by default.
-Wconstexpr-not-const
Warn if a non-constant expression is encountered when
really expecting a constant expression instead.
Currently, this warns when initializing an object of
static storage duration with an initializer which is not a
constant expression.
Sparse does not issue these warnings by default.
-Wcontext
Warn about potential errors in synchronization or other
delimited contexts.
Sparse supports several means of designating functions or
statements that delimit contexts, such as synchronization.
Functions with the extended attribute
__attribute__((context(expression,in_context,out_context))
require the context expression (for instance, a lock) to
have the value in_context (a constant nonnegative integer)
when called, and return with the value out_context (a
constant nonnegative integer). For APIs defined via
macros, use the statement form
__context__(expression,in_value,out_value) in the body of
the macro.
With -Wcontext Sparse will warn when it sees a function
change the context without indicating this with a context
attribute, either by decreasing a context below zero (such
as by releasing a lock without acquiring it), or returning
with a changed context (such as by acquiring a lock
without releasing it). Sparse will also warn about blocks
of code which may potentially execute with different
contexts.
Sparse issues these warnings by default. To turn them
off, use -Wno-context.
-Wdecl Warn about any non-static variable or function definition
that has no previous declaration.
Private symbols (functions and variables) internal to a
given source file should use static, to allow additional
compiler optimizations, allow detection of unused symbols,
and prevent other code from relying on these internal
symbols. Public symbols used by other source files will
need declarations visible to those other source files,
such as in a header file. All declarations should fall
into one of these two categories. Thus, with -Wdecl,
Sparse warns about any symbol definition with neither
static nor a declaration. To fix this warning, declare
private symbols static, and ensure that the files defining
public symbols have the symbol declarations available
first (such as by including the appropriate header file).
Sparse issues these warnings by default. To turn them
off, use -Wno-decl.
-Wdeclaration-after-statement
Warn about declarations that are not at the start of a
block.
These declarations are permitted in C99 but not in C89.
Sparse issues these warnings by default only when the C
dialect is C89 (i.e. -ansi or -std=c89). To turn them
off, use -Wno-declaration-after-statement.
-Wdefault-bitfield-sign
Warn about any bitfield with no explicit signedness.
Bitfields have no standard-specified default signedness.
(C99 6.7.2) A bitfield without an explicit signed or
unsigned creates a portability problem for software that
relies on the available range of values. To fix this,
specify the bitfield type as signed or unsigned
explicitly.
Sparse does not issue these warnings by default.
-Wdesignated-init
Warn about positional initialization of structs marked as
requiring designated initializers.
Sparse allows an attribute
__attribute__((designated_init)) which marks a struct as
requiring designated initializers. Sparse will warn about
positional initialization of a struct variable or struct
literal of a type that has this attribute.
Requiring designated initializers for a particular struct
type will insulate code using that struct type from
changes to the layout of the type, avoiding the need to
change initializers for that type unless they initialize a
removed or incompatibly changed field.
Common examples of this type of struct include collections
of function pointers for the implementations of a class of
related operations, for which the default NULL for an
unmentioned field in a designated initializer will
correctly indicate the absence of that operation.
Sparse issues these warnings by default. To turn them
off, use -Wno-designated-init.
-Wdo-while
Warn about do-while loops that do not delimit the loop
body with braces.
Sparse does not issue these warnings by default.
-Wenum-mismatch
Warn about the use of an expression of an incorrect enum
type when initializing another enum type, assigning to
another enum type, or passing an argument to a function
which expects another enum type.
Sparse issues these warnings by default. To turn them
off, use -Wno-enum-mismatch.
-Wexternal-function-has-definition
Warn about function definitions that are declared with
external linkage.
Sparse issues these warnings by default. To turn them
off, use -Wno-external-function-has-definition.
-Wflexible-array-array
Warn about arrays of structures containing a flexible
array.
Sparse issues these warnings by default. To turn them off,
use -Wno-flexible-array-array.
-Wflexible-array-nested
Warn about structures containing a flexible array being
contained into another structure, union or array.
Sparse does not issue these warnings by default.
-Wflexible-array-sizeof
Warn about using the sizeof operator on a structure
containing a flexible array, possibly recursively.
Sparse does not issue these warnings by default.
-Wflexible-array-union
Enable the warnings regarding flexible arrays and unions.
To have any effect, at least one of -Wflexible-array-
array, -Wflexible-array-nested or -Wflexible-array-sizeof
must also be enabled.
Sparse does issue these warnings by default.
-Winit-cstring
Warn about initialization of a char array with a too long
constant C string.
If the size of the char array and the length of the string
are the same, there is no space for the last nul char of
the string in the array:
char s[3] = "abc";
If the array is used as a byte array, not as C string,
this warning is just noise. However, if the array is
passed to functions dealing with C string like printf(%s)
and strcmp, it may cause a trouble.
Sparse does not issue these warnings by default.
-Wmemcpy-max-count
Warn about call of memcpy(), memset(), copy_from_user(),
or copy_to_user() with a large compile-time byte count.
Sparse issues these warnings by default. To turn them off,
use -Wno-memcpy-max-count.
The limit can be changed with -fmemcpy-max-count=COUNT,
the default being 100000.
-Wnewline-eof
Warn if the input file doesn't end with a newline.
Sparse issues these warnings by default. To turn them
off, use -Wno-newline-eof.
-Wnon-pointer-null
Warn about the use of 0 as a NULL pointer.
0 has integer type. NULL has pointer type.
Sparse issues these warnings by default. To turn them
off, use -Wno-non-pointer-null.
-Wold-initializer
Warn about the use of the pre-C99 GCC syntax for
designated initializers.
C99 provides a standard syntax for designated fields in
struct or union initializers:
struct structname var = { .field = value };
GCC also has an old, non-standard syntax for designated
initializers which predates C99:
struct structname var = { field: value };
Sparse will warn about the use of GCC's non-standard
syntax for designated initializers. To fix this warning,
convert designated initializers to use the standard C99
syntax.
Sparse issues these warnings by default. To turn them
off, use -Wno-old-initializer.
-Wone-bit-signed-bitfield
Warn about any one-bit signed bitfields.
A one-bit signed bitfield can only have the values 0 and
-1, or with some compilers only 0; this results in
unexpected behavior for programs which expected the
ability to store 0 and 1.
Sparse issues these warnings by default. To turn them
off, use -Wno-one-bit-signed-bitfield.
-Wparen-string
Warn about the use of a parenthesized string to initialize
an array.
Standard C syntax does not permit a parenthesized string
as an array initializer. GCC allows this syntax as an
extension. With -Wparen-string, Sparse will warn about
this syntax.
Sparse does not issue these warnings by default.
-Wpast-deep-designator
Warn when, in a initializer-list, a initializer with a
deep (nested) designator is followed by a non-designated
one.
Sparse does not issue these warnings by default.
-Wpointer-arith
Warn about anything that depends on the sizeof a void or
function type.
C99 does not allow the sizeof operator to be applied to
function types or to incomplete types such as void. GCC
allows sizeof to be applied to these types as an extension
and assigns these types a size of 1. With -pointer-arith,
Sparse will warn about pointer arithmetic on void or
function pointers, as well as expressions which directly
apply the sizeof operator to void or function types.
Sparse does not issue these warnings by default.
-Wptr-subtraction-blows
Warn when subtracting two pointers to a type with a non-
power-of-two size.
Subtracting two pointers to a given type gives a
difference in terms of the number of items of that type.
To generate this value, compilers will usually need to
divide the difference by the size of the type, an
potentially expensive operation for sizes other than
powers of two.
Code written using pointer subtraction can often use
another approach instead, such as array indexing with an
explicit array index variable, which may allow compilers
to generate more efficient code.
Sparse does not issue these warnings by default.
-Wreturn-void
Warn if a function with return type void returns a void
expression.
C99 permits this, and in some cases this allows for more
generic code in macros that use typeof or take a type as a
macro argument. However, some programs consider this poor
style, and those programs can use -Wreturn-void to get
warnings about it.
Sparse does not issue these warnings by default.
-Wshadow
Warn when declaring a symbol which shadows a declaration
with the same name in an outer scope.
Such declarations can lead to error-prone code.
Sparse does not issue these warnings by default.
-Wshift-count-negative
Warn if a shift count is negative.
Sparse issues these warnings by default.
-Wshift-count-overflow
Warn if a shift count is bigger than the operand's width.
Sparse issues these warnings by default.
-Wsizeof-bool
Warn when checking the sizeof a _Bool.
C99 does not specify the size of a _Bool. GCC, by default,
uses 1.
Sparse does not issue these warnings by default.
-Wtransparent-union
Warn about any declaration using the GCC extension
__attribute__((transparent_union)).
Sparse issues these warnings by default. To turn them
off, use -Wno-transparent-union.
-Wtypesign
Warn when converting a pointer to an integer type into a
pointer to an integer type with different signedness.
Sparse does not issue these warnings by default.
-Wundef
Warn about preprocessor conditionals that use the value of
an undefined preprocessor symbol.
Standard C (C99 6.10.1) permits using the value of an
undefined preprocessor symbol in preprocessor
conditionals, and specifies it has a value of 0. However,
this behavior can lead to subtle errors.
Sparse does not issue these warnings by default.
-Wuniversal-initializer
Do not suppress warnings caused by using '{ 0 }' instead
of '{ }' on aggregate types, ignoring its special status
as universal initializer. The concerned warnings are, for
example, those triggered by -Wdesignated-init or
-Wnon-pointer-null.
Sparse does not issue these warnings by default,
processing '{ 0 }' the same as '{ }'.
-Wunion-cast
Warn on casts to union types.
Sparse does not issues these warnings by default.
--arch=ARCH
Specify the target architecture. For architectures having
both a 32-bit and a 64-bit variant (mips, powerpc, riscv
and sparc) the architecture name can be suffixed with 32
or 64.
The default architecture and size is the one of the
machine used to build Sparse.
-gcc-base-dir dir
Look for compiler-provided system headers in dir/include/
and dir/include-fixed/.
-multiarch-dir dir
Look for system headers in the multiarch subdirectory dir.
The dir name would normally take the form of the target's
normalized GNU triplet. (e.g. i386-linux-gnu).
--os=OS
Specify the target Operating System. This only makes a
few differences with the predefined types. The accepted
values are: linux, unix, freebsd, netbsd, opensd, sunos,
darwin and cygwin.
The default OS is the one of the machine used to build
Sparse if it can be detected, otherwise some generic
settings are used.
-fmem-report
Report some statistics about memory allocation used by the
tool.
-fdiagnostic-prefix[=PREFIX]
Prefix all diagnostics by the given PREFIX, followed by ":
". If no one is given "sparse" is used. The default is
to not use a prefix at all.
-fmemcpy-max-count=COUNT
Set the limit for the warnings given by -Wmemcpy-max-
count. A COUNT of 'unlimited' or '0' will effectively
disable the warning. The default limit is 100000.
-ftabstop=WIDTH
Set the distance between tab stops. This helps sparse
report correct column numbers in warnings or errors. If
the value is less than 1 or greater than 100, the option
is ignored. The default is 8.
-f[no-]unsigned-bitfields, -f[no-]signed-bitfields
Determine the signedness of bitfields declared without an
explicit sign ('signed' or 'unsigned'). By default such
bitfields are signed, like others plain integers.
-f[no-]unsigned-char, -f[no-]signed-char
Let plain 'char' be unsigned or signed. By default chars
are signed.
cgcc(1)
https://sparse.docs.kernel.org
linux-sparse@vger.kernel.org
Submission of patches and reporting of bugs, as well as
discussions related to Sparse, should be done via the mailing
list (linux-sparse@vger.kernel.org) where the development and
maintenance is primarily done. You do not have to be subscribed
to the list to send a message there.
Bugs can also be reported and tracked via the Linux kernel's
bugzilla:
http://bugzilla.kernel.org/enter_bug.cgi?component=Sparse&product=Tools
.
More documentation about Sparse can be found at
https://sparse.docs.kernel.org
Sparse was started by Linus Torvalds. The complete list of
contributors can be find at
https://www.openhub.net/p/sparse/contributors .
Luc Van Oostenryck is Sparse's current maintainer.
This page is part of the sparse (a Semantic Parser for C)
project. Information about the project can be found at
⟨https://sparse.wiki.kernel.org/⟩. If you have a bug report for
this manual page, send it to linux-sparse@vger.kernel.org. This
page was obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/devel/sparse/sparse.git⟩ on
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-02-03.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
sparse(1)
Pages that refer to this page: cgcc(1), semind(1)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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