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Eric Lilja
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 Posted: Wed Jan 26, 2005 12:18 pm Post subject: Warning about defined but not used for global variable |
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Hello, I have a few global variables in my program. One of them holds the
name of the application and it's defined in a header file globals.hpp (and
the point of definition also happen to be the point of declaration of this
variable, correct?):
static const char * g_application_name = "Tiny, class-based MDI Example";
In another source file, I'm including the header globals.hpp and I'm using
the variable g_application_name. I do, however, get the following warning
when building my program:
globals.hpp:12: warning: 'g_application_name' defined but not used
This warning is repeated for every file that includes globals.hpp, either
directly or indirectly.
However, if I change the type of g_application_name to const char * const,
the warning disappears.
So I guess that the proper way to define a global string variable that is
not to be written, only read, and should be shared for all source files is
to the define it with the type const char * const?
/ Eric
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alexmdac@hotmail.com
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| Posted: Wed Jan 26, 2005 12:30 pm Post subject: Re: Warning about defined but not used for global variable |
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Yes you should use const char * const. const char * means that the
string buffer is writable but the pointer itself is constant. You
should treat string literals as read-only.
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Matthias
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| Posted: Wed Jan 26, 2005 1:17 pm Post subject: Re: Warning about defined but not used for global variable |
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[email]alexmdac (AT) hotmail (DOT) com[/email] wrote:
| Quote: | Yes you should use const char * const. const char * means that the
string buffer is writable but the pointer itself is constant. You
should treat string literals as read-only.
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Hm isn't it the other way around? AFAIK const char* means that the
character data is constant, but the pointer to it isn't, whereas char*
const means that the character data is variable and the pointer constant.
Correct me if I'm wrong.
--
Regards,
Matthias
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scott urban
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| Posted: Sun Jan 30, 2005 5:22 pm Post subject: Re: Warning about defined but not used for global variable |
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On 2005-01-26, Eric Lilja <ericliljaNoSpam (AT) yahoo (DOT) com> wrote:
| Quote: | Hello, I have a few global variables in my program. One of them holds the
name of the application and it's defined in a header file globals.hpp (and
the point of definition also happen to be the point of declaration of this
variable, correct?):
static const char * g_application_name = "Tiny, class-based MDI Example";
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Lose the static keyword; with static you get a separate variable named
'g_application_name' local to each translation unit that includes that
header - not 'global' at all. Change it to extern:
extern const char * g_application_name;
And, in one cpp file:
const char * g_application_name = "Tiny, class-based MDI Example";
| Quote: | In another source file, I'm including the header globals.hpp and I'm using
the variable g_application_name. I do, however, get the following warning
when building my program:
globals.hpp:12: warning: 'g_application_name' defined but not used
This warning is repeated for every file that includes globals.hpp, either
directly or indirectly.
However, if I change the type of g_application_name to const char * const,
the warning disappears.
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I'm not sure what the rules are here - but for types like int:
const int name = 0;
in a header is used everywhere possibly in read only memory and doesn't
need to be set up like a global variable that might change. That
apparently applies to 'const char * const' too, at least for your
compiler.
| Quote: | So I guess that the proper way to define a global string variable that is
not to be written, only read, and should be shared for all source files is
to the define it with the type const char * const?
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I think I would still do it the proper way, with a an extern declaration
in the header and a single definition in one cpp. At a minimum, if you
change the name of your application, you won't have to recompile all
files that include the header.
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