Microchip Technology SW006023-2N Data Sheet
Compiler Command Line Driver
2012 Microchip Technology Inc.
DS51686E-page 65
3.9.5
Options for Controlling Warnings and Errors
Warnings are diagnostic messages that report constructions that are not inherently
erroneous, but that are risky or suggest there may have been an error.
erroneous, but that are risky or suggest there may have been an error.
You can request many specific warnings with options beginning -W; for example,
-Wimplicit,
-Wimplicit,
to request warnings on implicit declarations. Each of these specific
warning options also has a negative form beginning -Wno- to turn off warnings; for
example, -Wno-implicit. This manual lists only one of the two forms, whichever is
not the default.
example, -Wno-implicit. This manual lists only one of the two forms, whichever is
not the default.
The following options control the amount and kinds of warnings produced by the
compiler.
compiler.
TABLE 3-8:
WARNING AND ERROR OPTIONS IMPLIED BY ALL WARNINGS
Option
Definition
-fsyntax-only
Check the code for syntax, but don’t do anything beyond that.
-pedantic
Issue all the warnings demanded by strict ANSI C. Reject all
programs that use forbidden extensions.
programs that use forbidden extensions.
-pedantic-errors
Like -pedantic, except that errors are produced rather than
warnings.
warnings.
-w
Inhibit all warning messages.
-Wall
This enables all the warnings about constructions that some
users consider questionable, and that are easy to avoid (or
modify to prevent the warning), even in conjunction with macros.
Note that some warning flags are not implied by -Wall. Some of
them warn about constructions that users generally do not
consider questionable, but which occasionally you might wish to
check for; others warn about constructions that are necessary or
hard to avoid in some cases, and there is no simple way to
modify the code to suppress the warning. Some of them are
enabled by -Wextra but many of them must be enabled
individually.
users consider questionable, and that are easy to avoid (or
modify to prevent the warning), even in conjunction with macros.
Note that some warning flags are not implied by -Wall. Some of
them warn about constructions that users generally do not
consider questionable, but which occasionally you might wish to
check for; others warn about constructions that are necessary or
hard to avoid in some cases, and there is no simple way to
modify the code to suppress the warning. Some of them are
enabled by -Wextra but many of them must be enabled
individually.
-Waddress
Warn about suspicious uses of memory addresses. These
include using the address of a function in a conditional
expression, such as void func(void); if (func), and
comparisons against the memory address of a string literal, such
as if (x == "abc"). Such uses typically indicate a programmer
error: the address of a function always evaluates to true, so their
use in a conditional usually indicates that the programmer forgot
the parentheses in a function call; and comparisons against
string literals result in unspecified behavior and are not portable
in C, so they usually indicate that the programmer intended to
use strcmp.
include using the address of a function in a conditional
expression, such as void func(void); if (func), and
comparisons against the memory address of a string literal, such
as if (x == "abc"). Such uses typically indicate a programmer
error: the address of a function always evaluates to true, so their
use in a conditional usually indicates that the programmer forgot
the parentheses in a function call; and comparisons against
string literals result in unspecified behavior and are not portable
in C, so they usually indicate that the programmer intended to
use strcmp.
-Wchar-subscripts
Warn if an array subscript has type char.
-Wcomment
Warn whenever a comment-start sequence /* appears in a /*
comment, or whenever a Backslash-Newline appears in a //
comment.
comment, or whenever a Backslash-Newline appears in a //
comment.
-Wdiv-by-zero
Warn about compile-time integer division by zero. To inhibit the
warning messages, use -Wno-div-by-zero. Floating-point
division by zero is not warned about, as it can be a legitimate
way of obtaining infinities and NaNs.
(This is the default.)
warning messages, use -Wno-div-by-zero. Floating-point
division by zero is not warned about, as it can be a legitimate
way of obtaining infinities and NaNs.
(This is the default.)
-Wformat
Check calls to printf and scanf, etc., to make sure that the
arguments supplied have types appropriate to the format string
specified.
arguments supplied have types appropriate to the format string
specified.