1sparse(1) General Commands Manual sparse(1)
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6 sparse - Semantic Parser for C
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9 sparse [WARNING OPTIONS]... file.c
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12 Sparse parses C source and looks for errors, producing warnings on
13 standard error.
14 Sparse accepts options controlling the set of warnings to generate. To
16 turn on warnings Sparse does not issue by default, use the correspond‐
17 ing warning option -Wsomething. Sparse issues some warnings by
18 default; to turn off those warnings, pass the negation of the associ‐
19 ated warning option, -Wno-something.
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22 -Waddress-space
23 Warn about code which mixes pointers to different address spa‐
24 ces.
25 Sparse allows an extended attribute
27 __attribute__((address_space(num))) on pointers, which desig‐
28 nates a pointer target in address space num (a constant inte‐
29 ger). With -Waddress-space, Sparse treats pointers with identi‐
30 cal target types but different address spaces as distinct types.
31 To override this warning, such as for functions which convert
32 pointers between address spaces, use a type that includes
33 __attribute__((force)).
34 Sparse issues these warnings by default. To turn them off, use
36 -Wno-address-space.
37 -Wbitwise
39 Warn about unsupported operations or type mismatches with
40 restricted integer types.
41 Sparse supports an extended attribute, __attribute__((bitwise)),
43 which creates a new restricted integer type from a base integer
44 type, distinct from the base integer type and from any other
45 restricted integer type not declared in the same declaration or
46 typedef. For example, this allows programs to create typedefs
47 for integer types with specific endianness. With -Wbitwise,
48 Sparse will warn on any use of a restricted type in arithmetic
49 operations other than bitwise operations, and on any conversion
50 of one restricted type into another, except via a cast that
51 includes __attribute__((force)).
52 Sparse does not issue these warnings by default.
54 -Wcast-to-as
56 Warn about casts which add an address space to a pointer type.
57 A cast that includes __attribute__((force)) will suppress this
59 warning.
60 Sparse does not issue these warnings by default.
62 -Wcast-truncate
64 Warn about casts that truncate constant values.
65 Sparse issues these warnings by default. To turn them off, use
67 -Wno-cast-truncate.
68 -Wcontext
70 Warn about potential errors in synchronization or other delim‐
71 ited contexts.
72 Sparse supports several means of designating functions or state‐
74 ments that delimit contexts, such as synchronization. Functions
75 with the extended attribute __attribute__((context(expres‐
76 sion,in_context,out_context)) require the context expression
77 (for instance, a lock) to have the value in_context (a constant
78 nonnegative integer) when called, and return with the value
79 out_context (a constant nonnegative integer). For APIs defined
80 via macros, use the statement form __context__(expres‐
81 sion,in_value,out_value) in the body of the macro.
82 With -Wcontext Sparse will warn when it sees a function change
84 the context without indicating this with a context attribute,
85 either by decreasing a context below zero (such as by releasing
86 a lock without acquiring it), or returning with a changed con‐
87 text (such as by acquiring a lock without releasing it). Sparse
88 will also warn about blocks of code which may potentially exe‐
89 cute with different contexts.
90 Sparse issues these warnings by default. To turn them off, use
92 -Wno-context.
93 -Wdecl Warn about any non-static variable or function definition that
95 has no previous declaration.
96 Private symbols (functions and variables) internal to a given
98 source file should use static, to allow additional compiler
99 optimizations, allow detection of unused symbols, and prevent
100 other code from relying on these internal symbols. Public sym‐
101 bols used by other source files will need declarations visible
102 to those other source files, such as in a header file. All dec‐
103 larations should fall into one of these two categories. Thus,
104 with -Wdecl, Sparse warns about any symbol definition with nei‐
105 ther static nor a declaration. To fix this warning, declare
106 private symbols static, and ensure that the files defining pub‐
107 lic symbols have the symbol declarations available first (such
108 as by including the appropriate header file).
109 Sparse issues these warnings by default. To turn them off, use
111 -Wno-decl.
112 -Wdefault-bitfield-sign
114 Warn about any bitfield with no explicit signedness.
115 Bitfields have no standard-specified default signedness. (C99
117 6.7.2) A bitfield without an explicit signed or unsigned creates
118 a portability problem for software that relies on the available
119 range of values. To fix this, specify the bitfield type as
120 signed or unsigned explicitly.
121 Sparse does not issue these warnings by default.
123 -Wdo-while
125 Warn about do-while loops that do not delimit the loop body with
126 braces.
127 Sparse does not issue these warnings by default.
129 -Wenum-mismatch
131 Warn about the use of an expression of an incorrect enum type
132 when initializing another enum type, assigning to another enum
133 type, or passing an argument to a function which expects another
134 enum type.
135 Sparse issues these warnings by default. To turn them off, use
137 -Wno-enum-mismatch.
138 -Wnon-pointer-null
140 Warn about the use of 0 as a NULL pointer.
141 0 has integer type. NULL has pointer type.
143 Sparse issues these warnings by default. To turn them off, use
145 -Wno-non-pointer-null.
146 -Wold-initializer
148 Warn about the use of the pre-C99 GCC syntax for designated ini‐
149 tializers.
150 C99 provides a standard syntax for designated fields in struct
152 or union initializers:
153 struct structname var = { .field = value };
155 GCC also has an old, non-standard syntax for designated initial‐
157 izers which predates C99:
158 struct structname var = { field: value };
160 Sparse will warn about the use of GCC's non-standard syntax for
162 designated initializers. To fix this warning, convert desig‐
163 nated initializers to use the standard C99 syntax.
164 Sparse issues these warnings by default. To turn them off, use
166 -Wno-old-initializer.
167 -Wone-bit-signed-bitfield
169 Warn about any one-bit signed bitfields.
170 A one-bit signed bitfield can only have the values 0 and -1, or
172 with some compilers only 0; this results in unexpected behavior
173 for programs which expected the ability to store 0 and 1.
174 Sparse issues these warnings by default. To turn them off, use
176 -Wno-one-bit-signed-bitfield.
177 -Wparen-string
179 Warn about the use of a parenthesized string to initialize an
180 array.
181 Standard C syntax does not permit a parenthesized string as an
183 array initializer. GCC allows this syntax as an extension.
184 With -Wparen-string, Sparse will warn about this syntax.
185 Sparse does not issue these warnings by default.
187 -Wptr-subtraction-blows
189 Warn when subtracting two pointers to a type with a non-power-
190 of-two size.
191 Subtracting two pointers to a given type gives a difference in
193 terms of the number of items of that type. To generate this
194 value, compilers will usually need to divide the difference by
195 the size of the type, an potentially expensive operation for
196 sizes other than powers of two.
197 Code written using pointer subtraction can often use another
199 approach instead, such as array indexing with an explicit array
200 index variable, which may allow compilers to generate more effi‐
201 cient code.
202 Sparse does not issue these warnings by default.
204 -Wreturn-void
206 Warn if a function with return type void returns a void expres‐
207 sion.
208 C99 permits this, and in some cases this allows for more generic
210 code in macros that use typeof or take a type as a macro argu‐
211 ment. However, some programs consider this poor style, and
212 those programs can use -Wreturn-void to get warnings about it.
213 Sparse does not issue these warnings by default.
215 -Wshadow
217 Warn when declaring a symbol which shadows a declaration with
218 the same name in an outer scope.
219 Such declarations can lead to error-prone code.
221 Sparse does not issue these warnings by default.
223 -Wtransparent-union
225 Warn about any declaration using the GCC extension
226 __attribute__((transparent_union)).
227 Sparse issues these warnings by default. To turn them off, use
229 -Wno-transparent-union.
230 -Wtypesign
232 Warn when converting a pointer to an integer type into a pointer
233 to an integer type with different signedness.
234 Sparse does not issue these warnings by default.
236 -Wundef
238 Warn about preprocessor conditionals that use the value of an
239 undefined preprocessor symbol.
240 Standard C (C99 6.10.1) permits using the value of an undefined
242 preprocessor symbol in preprocessor conditionals, and specifies
243 it has have a value of 0. However, this behavior can lead to
244 subtle errors.
245 Sparse does not issue these warnings by default.
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249 cgcc(1)
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252 http://www.kernel.org/pub/software/devel/sparse/
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255 linux-sparse@vger.kernel.org
256
258 Josh Triplett <josh@kernel.org>
259 sparse(1)