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Altera_Forum
Honored Contributor I
1,077 Views

Using GCC compiler warning "-Wempty-body"

I added -Wextra to my build to make the code cleaner. But I get an "Empty body in an else statement" warning which -Wextra does enable (see: http://gcc.gnu.org/onlinedocs/gcc/warning-options.html#warning-options). 

 

So I added -Wno-empty-body to the NIOS II compiler warnings text line and I get this error: cc1.exe: error: unrecognized command line option "-Wno-empty-body". I also get the error using -Wempty-body. 

 

So the question is, what is the right option for this warning? 

 

Thanks, 

Bill
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6 Replies
Altera_Forum
Honored Contributor I
131 Views

Check the documentation for the version of gcc you are using, -Wempty-body is probably a very new option.

Altera_Forum
Honored Contributor I
131 Views

I thought that might be the case. I know the NIOS II GCC compiler (4.x?) is behind the latest GCC release. So does this mean the NIOS II GCC compiler generates the warning without any way to disable it? 

 

Thanks dsl! 

Bill
Altera_Forum
Honored Contributor I
131 Views

A quick look in the gcc sources (having repoduced the error message with a random gcc 4.1.2 since you misquoted it) shows it being generated in c_finish_if_stmt() in c-typeck.c. 

 

The code is inside 'if (extra_warnings)' - probably set by -Wextra, and is: 

warning (0, "%Hempty body in an else-statement", EXPR_LOCUS (*inner_else));Compare this against, a few lines higher: 

warning (OPT_Wparentheses, "%Hsuggest explicit braces to avoid ambiguous %<else%>", &if_locus);My guess is that the first argument to warning() maps onto the flag to enable/disable the warning. 

 

So you are probably out of luck.
Altera_Forum
Honored Contributor I
131 Views

Wow, thanks for the research! Much appreciated. I think you're right - the 0 argument is telling. I guess the next step is to explicitly call out the -W options excluding empty_body that -Wextra turns on. Like: 

 

-Wclobbered -Wignored-qualifiers -Wmissing-field-initializers -Wmissing-parameter-type -Wold-style-declaration -Woverride-init -Wsign-compare -Wtype-limits -Wuninitialized -Wunused-parameter -Wunused-but-set-parameter 

 

I tried the above options. LOL - 7 of these aren't recognized! Oh well. 

 

Thanks again, 

Bill
Altera_Forum
Honored Contributor I
131 Views

There is an option to the compiler to list the known -W (etc) options. 

The gcc docs web site does have info for (some) older versions.
Altera_Forum
Honored Contributor I
131 Views

missing-field-initialisers and unused-parameter are somewhat horrid, fixing 'sign-compare' is bad enough

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