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Add infrastructure for compile-time assertions about variable types.

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Currently, the macros only work with fairly recent gcc versions, but there
is room to expand them to other compilers that have comparable features.

Heavily revised and autoconfiscated version of a patch by Andres Freund.
This commit is contained in:
Tom Lane
2012-09-30 14:38:31 -04:00
parent 26fd82ddf1
commit ea473fb2de
6 changed files with 214 additions and 0 deletions
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41
src/include/c.h
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@ -689,6 +689,47 @@ typedef NameData *Name;
} while (0)
/*
* Macros to support compile-time assertion checks, if the compiler has them.
*
* If the "condition" (a compile-time-constant expression) evaluates to false,
* throw a compile error using the "errmessage" (a string literal).
*
* gcc 4.6 and up supports _Static_assert(), but it has bizarre syntactic
* placement restrictions. These macros make it safe to use as a statement
* or in an expression, respectively.
*/
#ifdef HAVE__STATIC_ASSERT
#define StaticAssertStmt(condition, errmessage) \
do { _Static_assert(condition, errmessage); } while(0)
#define StaticAssertExpr(condition, errmessage) \
({ StaticAssertStmt(condition, errmessage); true; })
#else /* !HAVE__STATIC_ASSERT */
#define StaticAssertStmt(condition, errmessage)
#define StaticAssertExpr(condition, errmessage) ((void) true)
#endif /* HAVE__STATIC_ASSERT */
/*
* Compile-time checks that a variable (or expression) has the specified type.
*
* AssertVariableIsOfType() can be used as a statement.
* AssertVariableIsOfTypeMacro() is intended for use in macros, eg
* #define foo(x) (AssertVariableIsOfTypeMacro(x, int), bar(x))
*/
#ifdef HAVE__BUILTIN_TYPES_COMPATIBLE_P
#define AssertVariableIsOfType(varname, typename) \
StaticAssertStmt(__builtin_types_compatible_p(__typeof__(varname), typename), \
CppAsString(varname) " does not have type " CppAsString(typename))
#define AssertVariableIsOfTypeMacro(varname, typename) \
StaticAssertExpr(__builtin_types_compatible_p(__typeof__(varname), typename), \
CppAsString(varname) " does not have type " CppAsString(typename))
#else /* !HAVE__BUILTIN_TYPES_COMPATIBLE_P */
#define AssertVariableIsOfType(varname, typename)
#define AssertVariableIsOfTypeMacro(varname, typename) ((void) true)
#endif /* HAVE__BUILTIN_TYPES_COMPATIBLE_P */
/* ----------------------------------------------------------------
* Section 7: random stuff
* ----------------------------------------------------------------

6
src/include/pg_config.h.in
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@ -635,6 +635,12 @@
/* Define to 1 if you have the <winldap.h> header file. */
#undef HAVE_WINLDAP_H
/* Define to 1 if your compiler understands __builtin_types_compatible_p. */
#undef HAVE__BUILTIN_TYPES_COMPATIBLE_P
/* Define to 1 if your compiler understands _Static_assert. */
#undef HAVE__STATIC_ASSERT
/* Define to the appropriate snprintf format for 64-bit ints. */
#undef INT64_FORMAT

6
src/include/pg_config.h.win32
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@ -526,6 +526,12 @@
/* Define to 1 if you have the <winldap.h> header file. */
/* #undef HAVE_WINLDAP_H */
/* Define to 1 if your compiler understands __builtin_types_compatible_p. */
/* #undef HAVE__BUILTIN_TYPES_COMPATIBLE_P */
/* Define to 1 if your compiler understands _Static_assert. */
/* #undef HAVE__STATIC_ASSERT */
/* Define to the appropriate snprintf format for 64-bit ints, if any. */
#define INT64_FORMAT "%lld"