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Don't use STATIC_ASSERT_EXPR on non-GCC-compatible compilers

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ARRAY_LENGTH has a portable but unsafe implementation, and a
non-portable implementation that causes a compile-time error if the
macro is accidentally used on a pointer.

The safety check was only implemented for __GCC__-defining compilers,
but the part that triggered the compile-time error was always used. It
turns out that this part triggers a build warning with MSVC (at least
with some versions: observed with Visual Studio 2013).
```
C:\builds\workspace\mbed-tls-pr-head_PR-4141-head\src\tests\src\psa_crypto_helpers.c(52): error C2220: warning treated as error - no 'object' file generated [C:\builds\workspace\mbed-tls-pr-head_PR-4141-head\src\mbedtls_test.vcxproj]
C:\builds\workspace\mbed-tls-pr-head_PR-4141-head\src\tests\src\psa_crypto_helpers.c(52): warning C4116: unnamed type definition in parentheses [C:\builds\workspace\mbed-tls-pr-head_PR-4141-head\src\mbedtls_test.vcxproj]
```

Since a compile-time error is never triggered when the compile-time
check for the argument type is not implemented, just use the unsafe
macro directly when there's no safety check.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2021-02-15 12:17:00 +01:00
parent 6b362e6f01
commit c86a16548c
1 changed files with 19 additions and 14 deletions
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33
tests/include/test/macros.h
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@ -321,40 +321,45 @@
mbedtls_exit( 1 ); \
}
/** \def ARRAY_LENGTH
* Return the number of elements of a static or stack array.
*
* \param array A value of array (not pointer) type.
*
* \return The number of elements of the array.
*/
/* A correct implementation of ARRAY_LENGTH, but which silently gives
* a nonsensical result if called with a pointer rather than an array. */
#define ARRAY_LENGTH_UNSAFE( array ) \
( sizeof( array ) / sizeof( *( array ) ) )
#if defined(__GNUC__)
/* Test if arg and &(arg)[0] have the same type. This is true if arg is
* an array but not if it's a pointer. */
#define IS_ARRAY_NOT_POINTER( arg ) \
( ! __builtin_types_compatible_p( __typeof__( arg ), \
__typeof__( &( arg )[0] ) ) )
#else
/* On platforms where we don't know how to implement this check,
* omit it. Oh well, a non-portable check is better than nothing. */
#define IS_ARRAY_NOT_POINTER( arg ) 1
#endif
/* A compile-time constant with the value 0. If `const_expr` is not a
* compile-time constant with a nonzero value, cause a compile-time error. */
#define STATIC_ASSERT_EXPR( const_expr ) \
( 0 && sizeof( struct { unsigned int STATIC_ASSERT : 1 - 2 * ! ( const_expr ); } ) )
/* Return the scalar value `value` (possibly promoted). This is a compile-time
* constant if `value` is. `condition` must be a compile-time constant.
* If `condition` is false, arrange to cause a compile-time error. */
#define STATIC_ASSERT_THEN_RETURN( condition, value ) \
( STATIC_ASSERT_EXPR( condition ) ? 0 : ( value ) )
#define ARRAY_LENGTH_UNSAFE( array ) \
( sizeof( array ) / sizeof( *( array ) ) )
/** Return the number of elements of a static or stack array.
*
* \param array A value of array (not pointer) type.
*
* \return The number of elements of the array.
*/
#define ARRAY_LENGTH( array ) \
( STATIC_ASSERT_THEN_RETURN( IS_ARRAY_NOT_POINTER( array ), \
ARRAY_LENGTH_UNSAFE( array ) ) )
#else
/* If we aren't sure the compiler supports our non-standard tricks,
* fall back to the unsafe implementation. */
#define ARRAY_LENGTH( array ) ARRAY_LENGTH_UNSAFE( array )
#endif
/** Return the smaller of two values.
*
* \param x An integer-valued expression without side effects.