sparse.1 - pub/scm/devel/sparse/chrisl/sparse - Git at Google

 .\" Sparse manpage by Josh Triplett
 .TH sparse "1"
 .
 .SH NAME
 sparse \- Semantic Parser for C
 .
 .SH SYNOPSIS
 .B sparse
 [\fIWARNING OPTIONS\fR]... \fIfile.c\fR
 .
 .SH DESCRIPTION
 Sparse parses C source and looks for errors, producing warnings on standard
 error.
 .P
 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 \fB\-Wsomething\fR.  Sparse issues some warnings by default; to turn
 off those warnings, pass the negation of the associated warning option,
 \fB\-Wno\-something\fR.
 .
 .SH WARNING OPTIONS
 .TP
 .B \-Wsparse\-all
 Turn on all sparse warnings, except for those explicitly disabled via
 \fB\-Wno\-something\fR.
 .TP
 .B \-Waddress\-space
 Warn about code which mixes pointers to different address spaces.

 Sparse allows an extended attribute
 .BI __attribute__((address_space( num )))
 on pointers, which designates a pointer target in address space \fInum\fR (a
 constant integer).  With \fB\-Waddress\-space\fR, Sparse treats pointers with
 identical target types but different address spaces as distinct types.  To
 override this warning, such as for functions which convert pointers between
 address spaces, use a type that includes \fB__attribute__((force))\fR.

 Sparse issues these warnings by default.  To turn them off, use
 \fB\-Wno\-address\-space\fR.
 .
 .TP
 .B \-Wbitwise
 Warn about unsupported operations or type mismatches with restricted integer
 types.

 Sparse supports an extended attribute, \fB__attribute__((bitwise))\fR, 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 \fBtypedef\fR.  For example, this allows programs
 to create \fBtypedef\fRs for integer types with specific endianness.  With
 \fB-Wbitwise\fR, 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
 \fB__attribute__((force))\fR.

 Sparse does not issue these warnings by default.
 .
 .TP
 .B \-Wcast\-to\-as
 Warn about casts which add an address space to a pointer type.

 A cast that includes \fB__attribute__((force))\fR will suppress this warning.

 Sparse does not issue these warnings by default.
 .
 .TP
 .B \-Wcast\-truncate
 Warn about casts that truncate constant values.

 Sparse issues these warnings by default.  To turn them off, use
 \fB\-Wno\-cast\-truncate\fR.
 .
 .TP
 .B \-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
 .BI __attribute__((context( expression , in_context , out_context ))
 require the context \fIexpression\fR (for instance, a lock) to have the value
 \fIin_context\fR (a constant nonnegative integer) when called, and return with
 the value \fIout_context\fR (a constant nonnegative integer).  For APIs
 defined via macros, use the statement form
 .BI __context__( expression , in_value , out_value )
 in the body of the macro.

 With \fB-Wcontext\fR Sparse will warn when it sees a function change the
 context without indicating this with a \fBcontext\fR 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
 \fB\-Wno\-context\fR.
 .
 .TP
 .B \-Wdecl
 Warn about any non-\fBstatic\fR variable or function definition that has no
 previous declaration.

 Private symbols (functions and variables) internal to a given source file
 should use \fBstatic\fR, 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
 \fB-Wdecl\fR, Sparse warns about any symbol definition with neither
 \fBstatic\fR nor a declaration.  To fix this warning, declare private symbols
 \fBstatic\fR, 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
 \fB\-Wno\-decl\fR.
 .
 .TP
 .B \-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
 \fB\-Wno\-declaration\-after\-statement\fR.
 .
 .TP
 .B \-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 \fBsigned\fR or \fBunsigned\fR creates a
 portability problem for software that relies on the available range of values.
 To fix this, specify the bitfield type as \fBsigned\fR or \fBunsigned\fR
 explicitly.

 Sparse does not issue these warnings by default.
 .
 .TP
 .B \-Wdesignated\-init
 Warn about positional initialization of structs marked as requiring designated
 initializers.

 Sparse allows an attribute
 .BI __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
 \fB\-Wno\-designated\-init\fR.
 .
 .TP
 .B \-Wdo\-while
 Warn about do-while loops that do not delimit the loop body with braces.

 Sparse does not issue these warnings by default.
 .
 .TP
 .B \-Wenum\-mismatch
 Warn about the use of an expression of an incorrect \fBenum\fR type when
 initializing another \fBenum\fR type, assigning to another \fBenum\fR type, or
 passing an argument to a function which expects another \fBenum\fR type.

 Sparse issues these warnings by default.  To turn them off, use
 \fB\-Wno\-enum\-mismatch\fR.
 .
 .TP
 .B \-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
 \fB\-Wno\-non\-pointer\-null\fR.
 .
 .TP
 .B \-Wold\-initializer
 Warn about the use of the pre-C99 GCC syntax for designated initializers.

 C99 provides a standard syntax for designated fields in \fBstruct\fR or
 \fBunion\fR initializers:

 .nf
 struct structname var = { .field = value };
 .fi

 GCC also has an old, non-standard syntax for designated initializers which
 predates C99:

 .nf
 struct structname var = { field: value };
 .fi

 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
 \fB\-Wno\-old\-initializer\fR.
 .
 .TP
 .B \-Wone\-bit\-signed\-bitfield
 Warn about any one-bit \fBsigned\fR bitfields.

 A one-bit \fBsigned\fR 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
 \fB\-Wno\-one\-bit\-signed\-bitfield\fR.
 .
 .TP
 .B \-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
 \fB\-Wparen\-string\fR, Sparse will warn about this syntax.

 Sparse does not issue these warnings by default.
 .
 .TP
 .B \-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.
 .
 .TP
 .B \-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
 \fB\-Wreturn\-void\fR to get warnings about it.

 Sparse does not issue these warnings by default.
 .
 .TP
 .B \-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.
 .
 .TP
 .B \-Wtransparent\-union
 Warn about any declaration using the GCC extension
 \fB__attribute__((transparent_union))\fR.

 Sparse issues these warnings by default.  To turn them off, use
 \fB\-Wno\-transparent\-union\fR.
 .
 .TP
 .B \-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.
 .
 .TP
 .B \-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 have a value of 0.
 However, this behavior can lead to subtle errors.

 Sparse does not issue these warnings by default.
 .
 .SH MISC OPTIONS
 .TP
 .B \-gcc-base-dir \fIdir\fR
 Look for compiler-provided system headers in \fIdir\fR/include/ and \fIdir\fR/include-fixed/.
 .
 .SH OTHER OPTIONS
 .TP
 .B \-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.
 .
 .SH SEE ALSO
 .BR cgcc (1)
 .
 .SH HOMEPAGE
 http://www.kernel.org/pub/software/devel/sparse/
 .
 .SH MAILING LIST
 linux-sparse@vger.kernel.org
 .
 .SH MAINTAINER
 Josh Triplett <josh@kernel.org>
	.\" Sparse manpage by Josh Triplett
	.TH sparse "1"
	.
	.SH NAME
	sparse \- Semantic Parser for C
	.
	.SH SYNOPSIS
	.B sparse
	[\fIWARNING OPTIONS\fR]... \fIfile.c\fR
	.
	.SH DESCRIPTION
	Sparse parses C source and looks for errors, producing warnings on standard
	error.
	.P
	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 \fB\-Wsomething\fR. Sparse issues some warnings by default; to turn
	off those warnings, pass the negation of the associated warning option,
	\fB\-Wno\-something\fR.
	.
	.SH WARNING OPTIONS
	.TP
	.B \-Wsparse\-all
	Turn on all sparse warnings, except for those explicitly disabled via
	\fB\-Wno\-something\fR.
	.TP
	.B \-Waddress\-space
	Warn about code which mixes pointers to different address spaces.

	Sparse allows an extended attribute
	.BI __attribute__((address_space( num )))
	on pointers, which designates a pointer target in address space \fInum\fR (a
	constant integer). With \fB\-Waddress\-space\fR, Sparse treats pointers with
	identical target types but different address spaces as distinct types. To
	override this warning, such as for functions which convert pointers between
	address spaces, use a type that includes \fB__attribute__((force))\fR.

	Sparse issues these warnings by default. To turn them off, use
	\fB\-Wno\-address\-space\fR.
	.
	.TP
	.B \-Wbitwise
	Warn about unsupported operations or type mismatches with restricted integer
	types.

	Sparse supports an extended attribute, \fB__attribute__((bitwise))\fR, 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 \fBtypedef\fR. For example, this allows programs
	to create \fBtypedef\fRs for integer types with specific endianness. With
	\fB-Wbitwise\fR, 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
	\fB__attribute__((force))\fR.

	Sparse does not issue these warnings by default.
	.
	.TP
	.B \-Wcast\-to\-as
	Warn about casts which add an address space to a pointer type.

	A cast that includes \fB__attribute__((force))\fR will suppress this warning.

	Sparse does not issue these warnings by default.
	.
	.TP
	.B \-Wcast\-truncate
	Warn about casts that truncate constant values.

	Sparse issues these warnings by default. To turn them off, use
	\fB\-Wno\-cast\-truncate\fR.
	.
	.TP
	.B \-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
	.BI __attribute__((context( expression , in_context , out_context ))
	require the context \fIexpression\fR (for instance, a lock) to have the value
	\fIin_context\fR (a constant nonnegative integer) when called, and return with
	the value \fIout_context\fR (a constant nonnegative integer). For APIs
	defined via macros, use the statement form
	.BI __context__( expression , in_value , out_value )
	in the body of the macro.

	With \fB-Wcontext\fR Sparse will warn when it sees a function change the
	context without indicating this with a \fBcontext\fR 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
	\fB\-Wno\-context\fR.
	.
	.TP
	.B \-Wdecl
	Warn about any non-\fBstatic\fR variable or function definition that has no
	previous declaration.

	Private symbols (functions and variables) internal to a given source file
	should use \fBstatic\fR, 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
	\fB-Wdecl\fR, Sparse warns about any symbol definition with neither
	\fBstatic\fR nor a declaration. To fix this warning, declare private symbols
	\fBstatic\fR, 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
	\fB\-Wno\-decl\fR.
	.
	.TP
	.B \-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
	\fB\-Wno\-declaration\-after\-statement\fR.
	.
	.TP
	.B \-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 \fBsigned\fR or \fBunsigned\fR creates a
	portability problem for software that relies on the available range of values.
	To fix this, specify the bitfield type as \fBsigned\fR or \fBunsigned\fR
	explicitly.

	Sparse does not issue these warnings by default.
	.
	.TP
	.B \-Wdesignated\-init
	Warn about positional initialization of structs marked as requiring designated
	initializers.

	Sparse allows an attribute
	.BI __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
	\fB\-Wno\-designated\-init\fR.
	.
	.TP
	.B \-Wdo\-while
	Warn about do-while loops that do not delimit the loop body with braces.

	Sparse does not issue these warnings by default.
	.
	.TP
	.B \-Wenum\-mismatch
	Warn about the use of an expression of an incorrect \fBenum\fR type when
	initializing another \fBenum\fR type, assigning to another \fBenum\fR type, or
	passing an argument to a function which expects another \fBenum\fR type.

	Sparse issues these warnings by default. To turn them off, use
	\fB\-Wno\-enum\-mismatch\fR.
	.
	.TP
	.B \-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
	\fB\-Wno\-non\-pointer\-null\fR.
	.
	.TP
	.B \-Wold\-initializer
	Warn about the use of the pre-C99 GCC syntax for designated initializers.

	C99 provides a standard syntax for designated fields in \fBstruct\fR or
	\fBunion\fR initializers:

	.nf
	struct structname var = { .field = value };
	.fi

	GCC also has an old, non-standard syntax for designated initializers which
	predates C99:

	.nf
	struct structname var = { field: value };
	.fi

	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
	\fB\-Wno\-old\-initializer\fR.
	.
	.TP
	.B \-Wone\-bit\-signed\-bitfield
	Warn about any one-bit \fBsigned\fR bitfields.

	A one-bit \fBsigned\fR 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
	\fB\-Wno\-one\-bit\-signed\-bitfield\fR.
	.
	.TP
	.B \-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
	\fB\-Wparen\-string\fR, Sparse will warn about this syntax.

	Sparse does not issue these warnings by default.
	.
	.TP
	.B \-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.
	.
	.TP
	.B \-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
	\fB\-Wreturn\-void\fR to get warnings about it.

	Sparse does not issue these warnings by default.
	.
	.TP
	.B \-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.
	.
	.TP
	.B \-Wtransparent\-union
	Warn about any declaration using the GCC extension
	\fB__attribute__((transparent_union))\fR.

	Sparse issues these warnings by default. To turn them off, use
	\fB\-Wno\-transparent\-union\fR.
	.
	.TP
	.B \-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.
	.
	.TP
	.B \-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 have a value of 0.
	However, this behavior can lead to subtle errors.

	Sparse does not issue these warnings by default.
	.
	.SH MISC OPTIONS
	.TP
	.B \-gcc-base-dir \fIdir\fR
	Look for compiler-provided system headers in \fIdir\fR/include/ and \fIdir\fR/include-fixed/.
	.
	.SH OTHER OPTIONS
	.TP
	.B \-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.
	.
	.SH SEE ALSO
	.BR cgcc (1)
	.
	.SH HOMEPAGE
	http://www.kernel.org/pub/software/devel/sparse/
	.
	.SH MAILING LIST
	linux-sparse@vger.kernel.org
	.
	.SH MAINTAINER
	Josh Triplett <josh@kernel.org>