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POWhy does gcc not warn when an enum or int value is passed on as a function's argument which is bool?
 

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  1. POWhy does gcc not warn when an enum or int value is passed on as a function's argument which is bool?
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    <p>I have following code:</p> <pre class="lang-c prettyprint-override"><code>typedef enum { FOO, BAR, BAZ } foo_t; static void afunc(bool is_it_on) { /* do the job */ } int main(void) { afunc(BAZ); return 0; } </code></pre> <p>Compiling this code does not generate any warning message, even with <code>-Wall -Wextra</code> options given to the compiler. I have even tried with <code>-Wconversion</code> option, which took no effect because <code>bool</code> and <code>enum</code> seemed to be of same size for g++. (the size of <code>enum</code> type is not defined in specification as far as I know)</p> <p>I have combed through gcc manual and found nothing about it.</p> <p>Questions:</p> <ul> <li>Is there a way to force the compiler to generate a warning in cases like this?</li> <li>Or is it that this implicit casting is legal by c++ specification?</li> </ul> <p>Compiler that I am using: gcc 4.1.2</p> <hr> <p><strong>Editted</strong></p> <p>Conclusion:</p> <p>The only viable solution to this seems to define a new type to represent 0 or 1, and use it instead of <code>bool</code>.</p> <p>The code would be like following, and g++ complains about type conversion:</p> <pre class="lang-c prettyprint-override"><code>typedef enum { FOO1, FOO2 } foo_t; typedef enum { MY_FALSE, MY_TRUE } my_bool_t; void foo(my_bool_t a) { } int main(void) { /* * gcc generates an error. * error: cannot convert ‘foo_t’ to ‘my_bool_t’ * for argument ‘1’ to ‘void foo(my_bool_t)’ */ foo(FOO1); return 0; } </code></pre>
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      1. POWhy does gcc not warn when an enum or int value is passed on as a function's argument which is bool?
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      1. USDavid Schwartz
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    1. COBecause C++’ type system is only good for user-defined types, for built-in types it invariably sucks. Consequence of its C heritage.
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      1. USKonrad Rudolph
    2. COYes it seems so. I've decided to typedef a new type dedicated to represent only 0 or 1, and use it instead of bool which seems to be intended to express _true_ or _false_.
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