Error Handling

Intel® C++ Compiler Classic Developer Guide and Reference

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ID 767249

Date 12/16/2022

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Error Handling

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

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

Some warnings that start with -W can be disabled using the negative form of the option -Wno-. For example, option -Wno-unknown-pragmas disables option -Wunknown-pragmas.

Linux and macOS

Additional Warnings

The following Linux* and macOS 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.

The following are some representative error messages:

missing closing quote

expression must have arithmetic type

expected a ";"

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

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

Example

Linux and macOS

-diag-disable=117,230,450

Windows

/Qdiag-disable:117,230,450

Option Summary

You can use the following compiler options to control remarks, warnings, and errors.

Linux and macOS

Option	Result
-w	Enables diagnostics for errors; disables diagnostics for warnings.
-w1	Enables diagnostics for warnings and errors.
-w2	Enables diagnostics for verbose warnings, warnings, and errors.
-w3	Enables diagnostics for remarks, warnings, and errors. Additional warnings are also enabled above level 2 warnings.
-Wremarks	Display remarks and comments.
-Wbrief	Display brief one-line diagnostics.
-Wcheck	Enable more strict diagnostics.
-Werror-all	Change all warnings and remarks to errors.
-Werror	Change all warnings to errors.

Windows

Option	Result
/W0	Enables diagnostics for errors; disables diagnostics for warnings.
/W1, /W2	Enables diagnostics for warnings and errors.
/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.
/WL	Display brief one-line diagnostics.
/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 macOS systems), or 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.

Parent topic: Compiler Reference

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Error Handling

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Option Summary