Remarks, Warnings, and Errors

This topic describes compiler remarks, warnings, and errors. The Intel® C++ Compiler sends these messages, along with the erroneous source line, to stderr.

Remarks

Remark messages report common but sometimes unconventional use of C or C++. Remarks do not stop translation or linking. Remarks do not interfere with any output files. The following are some representative remark messages:

function declared implicitly.
type qualifiers are meaningless in this declaration.
controlling expression is constant.

Warnings

Warning messages report legal but questionable use of C or C++. The compiler displays warnings by default. You can suppress warning messages by specifying an appropriate compiler option. Warnings do not stop translation or linking. Warnings do not interfere with any output files. The following are some representative warning messages:

declaration does not declare anything.
pointless comparison of unsigned integer with zero.
possible use of = where == was intended.

Additional Warnings

The following Linux* and OS X* options produce additional warnings:

Option	Result
-W[no-]missing-prototypes	Warn for missing prototypes.
-W[no-]missing-declarations	Warn for missing declarations.
-W[no-]unused-variable	Warn for unused variable.
-W[no-]pointer-arith	Warn for questionable pointer arithmetic.
-W[no-]uninitialized	Warn if a variable is used before being initialized.
-W[no-]deprecated	Display warnings related to deprecated features.
-W[no-]abi	Warn if generated code is not C++ ABI compliant.
-W[no-]unused-function	Warn if declared function is not used.
-W[no-]unknown-pragmas	Warn if an unknown `#pragma` directive is used.
-W[no-]main	Warn if return type of main is not expected.
-W[no-]comment[s]	Warn when /* appears in the middle of a /* */ comment.
-W[no-]return-type	Warn when a function uses the default int return type Warn when a return statement is used in a void function.

Errors

These messages report syntactic or semantic misuse of C or C++. The compiler always displays error messages. Errors suppress object code for the module containing the error and prevent linking, but they allow parsing to continue to detect other possible errors. Some representative error messages are:

missing closing quote.
expression must have arithmetic type.
expected a ";".

Some remarks, warnings, and errors are numbered and can be disabled using option -diag-disable=list or /Qdiag-disable:list.

Example
// Windows* /Qdiag-disable:117,230,450
// Linux* and OS X* -diag-disable=117,230,450

Option Summary

Use the following compiler options to control remarks, warnings, and errors (Note: options with a '-' prefix supported on Linux* and OS X* and options with a '/' prefix supported on Windows*):

Option	Result
-w, /W0	Enables diagnostics for errors; disables diagnostics for warnings.
-w1, /W1, /W2	Enables diagnostics for warnings and errors.
-w2	Enables diagnostics for verbose warnings, warnings, and errors.
-w3, /W3	Enables diagnostics for remarks, warnings, and errors. Additional warnings are also enabled above level 2 warnings.
/W4, /Wall	Enables diagnostics for all level 3 warnings, plus informational warnings and remarks, which, in most cases, can be safely ignored.
/W5	Enables diagnostics for all remarks, warnings, and errors. This option produces the most diagnostic messages.
-Wremarks	Display remarks and comments.
-Wbrief, /WL	Display brief one-line diagnostics.
-Wcheck	Enable more strict diagnostics.
-Werror-all	Change all warnings and remarks to errors.
-Werror, /WX	Change all warnings to errors.
/Wp64	Display diagnostics for 64-bit porting.

You can also control the display of diagnostic information with variations of the [Q]diag compiler option. This compiler option accepts numerous arguments and values, allowing you wide control over displayed diagnostic messages and reports.

Some of the most common variations include the following:

Option	Result
[Q]diag-enable<:\|=>`list`	Enables a diagnostic message or a group of messages.
[Q]diag-disable<:\|=>`list`	Disables a diagnostic message or a group of messages.
[Q]diag-warning<:\|=>`list`	Tells the compiler to change diagnostics to warnings.
[Q]diag-error<:\|=>`list`	Tells the compiler to change diagnostics to errors.
[Q]diag-remark<:\|=>`list`	Tells the compiler to change diagnostics to remarks (comments).

The list items can be specific diagnostic IDs, one of the keywords warn, remark, or error, or a keyword specifying a certain group (par, vec, driver, thread, port-linux (available on Windows* systems), port-win (available on Linux* and OS X* systems), openmp). For more information, see [Q]diag.

Other diagnostic-related options include the following:

Option	Result
[Q]diag-dump	Tells the compiler to print all enabled diagnostic messages and stop compilation.
[Q]diag-file[<:\|=>`file`]	Causes the results of diagnostic analysis to be output to a file.
[Q]diag-file-append[<:\|=>`file`]	Causes the results of diagnostic analysis to be appended to a file.
[Q]diag-error-limit<:\|=>`n`	Specifies the maximum number of errors allowed before compilation stops.