1 /* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */ 2 #ifndef PLDM_COMPILER_H 3 #define PLDM_COMPILER_H 4 5 #ifndef __has_attribute 6 #error The libpldm implementation requires __has_attribute 7 #endif 8 9 #include <assert.h> 10 11 static struct { 12 static_assert(__has_attribute(unused), 13 "`unused` attribute is required"); 14 int compliance; 15 } pldm_required_attributes __attribute__((unused)); 16 17 #define LIBPLDM_CC_UNUSED __attribute__((unused)) 18 19 // NOLINTBEGIN(bugprone-macro-parentheses) 20 /** 21 * Require that the given object is of the specified type. 22 * 23 * If the object is not of the required type then a diagnostic will be emitted. 24 * 25 * If you are reading this documentation due to hitting a compilation error 26 * passing through the macro, then you have a type error in your code that must 27 * be fixed. Despite the compiler output, the error is _not_ that some array 28 * is negatively sized, the array is negatively sized _because_ you have a type 29 * error. 30 * 31 * How this works: 32 * 33 * If the type of @p obj is not equivalent to the provided type @p type then 34 * we force the compiler to evaluate sizeof on a negatively-sized array. The 35 * C standard requires that the integer constant expression that specifies 36 * the array length must be greater than zero. Failure to meet this constraint 37 * generally terminates compilation of the translation unit as any other result 38 * cannot be handled in a sensible way. The array size is derived to an integer 39 * constant expression from a type eqivalence evaluated using _Generic() 40 * allowing us to stay within the language standard. The default generic 41 * association, representing a type mismatch, yields -1. 42 * 43 * pldm_require_obj_type() was introduced into the libpldm implementation to 44 * enable use of the pldm_msgbuf_extract*() APIs for objects that may or may not 45 * reside in a packed struct. See src/msgbuf.h for more details. 46 * 47 * @param obj The name of the object to evaluate 48 * @param type The required type of @p obj 49 * 50 * @return The expression either yields 1, or compilation is terminated 51 */ 52 #define pldm_require_obj_type(obj, type) \ 53 ((void)(sizeof( \ 54 struct { char buf[_Generic((obj), type: 1, default: -1)]; }))) 55 // NOLINTEND(bugprone-macro-parentheses) 56 57 #endif 58