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Diffstat (limited to 'shared/c-stdaux/src/c-stdaux.h')
| -rw-r--r-- | shared/c-stdaux/src/c-stdaux.h | 546 |
1 files changed, 546 insertions, 0 deletions
diff --git a/shared/c-stdaux/src/c-stdaux.h b/shared/c-stdaux/src/c-stdaux.h new file mode 100644 index 00000000..08d155ce --- /dev/null +++ b/shared/c-stdaux/src/c-stdaux.h @@ -0,0 +1,546 @@ +#pragma once + +/* + * Auxiliary macros and functions for the C standard library + * + * The `c-stdaux.h` header contains a collection of auxiliary macros and helper + * functions around the functionality provided by the different C standard + * library implementations, as well as other specifications implemented by + * them. + * + * Most of the helpers provided here provide aliases for common library and + * compiler features. Furthermore, several helpers simply provide other calling + * conventions than their standard counterparts (e.g., they allow for NULL to + * be passed with an object length of 0 where it makes sense to accept empty + * input). + * + * The namespace used by this project is: + * + * * `c_*` for all common C symbols or definitions that behave like proper C + * entities (e.g., macros that protect against double-evaluation would use + * lower-case names) + * + * * `C_*` for all constants, as well as macros that may not be safe against + * double evaluation. + */ + +#ifdef __cplusplus +extern "C" { +#endif + +#include <assert.h> +#include <dirent.h> +#include <errno.h> +#include <fcntl.h> +#include <inttypes.h> +#include <limits.h> +#include <stdalign.h> +#include <stdarg.h> +#if 0 /* NM_IGNORED */ +#include <stdatomic.h> +#endif /* NM_IGNORED */ +#include <stdbool.h> +#include <stddef.h> +#include <stdio.h> +#include <stdlib.h> +#include <stdnoreturn.h> +#include <string.h> +#include <sys/time.h> +#include <sys/types.h> +#include <time.h> +#include <unistd.h> + +/* + * Shortcuts for gcc attributes. See GCC manual for details. They're 1-to-1 + * mappings to the GCC equivalents. No additional magic here. They are + * supported by other compilers as well. + */ +#define _c_cleanup_(_x) __attribute__((__cleanup__(_x))) +#define _c_const_ __attribute__((__const__)) +#define _c_deprecated_ __attribute__((__deprecated__)) +#define _c_hidden_ __attribute__((__visibility__("hidden"))) +#define _c_likely_(_x) (__builtin_expect(!!(_x), 1)) +#define _c_packed_ __attribute__((__packed__)) +#define _c_printf_(_a, _b) __attribute__((__format__(printf, _a, _b))) +#define _c_public_ __attribute__((__visibility__("default"))) +#define _c_pure_ __attribute__((__pure__)) +#define _c_sentinel_ __attribute__((__sentinel__)) +#define _c_unlikely_(_x) (__builtin_expect(!!(_x), 0)) +#define _c_unused_ __attribute__((__unused__)) + +/** + * C_EXPR_ASSERT() - create expression with assertion + * @_expr: expression to evaluate to + * @_assertion: arbitrary assertion + * @_message: message associated with the assertion + * + * This macro simply evaluates to @_expr. That is, it can be used in any + * context that expects an expression like @_expr. Additionally, it takes an + * assertion as @_assertion and evaluates it through _Static_assert(), using + * @_message as debug message. + * + * The _Static_assert() builtin of C11 is defined as statement and thus cannot + * be used in expressions. This macro circumvents this restriction. + * + * Return: Evaluates to @_expr. + */ +#define C_EXPR_ASSERT(_expr, _assertion, _message) \ + /* indentation and line-split to get better diagnostics */ \ + (__builtin_choose_expr( \ + !!(1 + 0 * sizeof( \ + struct { \ +_Static_assert(_assertion, _message); \ + } \ + )), \ + (_expr), \ + ((void)0) \ + )) + +/** + * C_STRINGIFY() - stringify a token, but evaluate it first + * @_x: token to evaluate and stringify + * + * Return: Evaluates to a constant string literal + */ +#define C_STRINGIFY(_x) C_INTERNAL_STRINGIFY(_x) +#define C_INTERNAL_STRINGIFY(_x) #_x + +/** + * C_CONCATENATE() - concatenate two tokens, but evaluate them first + * @_x: first token + * @_y: second token + * + * Return: Evaluates to a constant identifier + */ +#define C_CONCATENATE(_x, _y) C_INTERNAL_CONCATENATE(_x, _y) +#define C_INTERNAL_CONCATENATE(_x, _y) _x ## _y + +/** + * C_EXPAND() - expand a tuple to a series of its values + * @_x: tuple to expand + * + * Return: Evaluates to the expanded tuple + */ +#define C_EXPAND(_x) C_INTERNAL_EXPAND _x +#define C_INTERNAL_EXPAND(...) __VA_ARGS__ + +/** + * C_VAR() - generate unique variable name + * @_x: name of variable, optional + * @_uniq: unique prefix, usually provided by __COUNTER__, optional + * + * This macro shall be used to generate unique variable names, that will not be + * shadowed by recursive macro invocations. It is effectively a + * C_CONCATENATE of both arguments, but also provides a globally separated + * prefix and makes the code better readable. + * + * The second argument is optional. If not given, __LINE__ is implied, and as + * such the macro will generate the same identifier if used multiple times on + * the same code-line (or within a macro). This should be used if recursive + * calls into the macro are not expected. In fact, no argument is necessary in + * this case, as a mere `C_VAR` will evaluate to a valid variable name. + * + * This helper may be used by macro implementations that might reasonable well + * be called in a stacked fasion, like: + * + * c_max(foo, c_max(bar, baz)) + * + * Such a stacked call of c_max() might cause compiler warnings of shadowed + * variables in the definition of c_max(). By using C_VAR(), such warnings + * can be silenced as each evaluation of c_max() uses unique variable names. + * + * Return: This evaluates to a constant identifier. + */ +#define C_VAR(...) C_INTERNAL_VAR(__VA_ARGS__, 2, 1) +#define C_INTERNAL_VAR(_x, _uniq, _num, ...) C_VAR ## _num (_x, _uniq) +#define C_VAR1(_x, _unused) C_VAR2(_x, C_CONCATENATE(line, __LINE__)) +#define C_VAR2(_x, _uniq) C_CONCATENATE(c_internal_var_unique_, C_CONCATENATE(_uniq, _x)) + +/** + * C_CC_MACRO1() - provide safe environment to a macro + * @_call: macro to call + * @_x1: first argument + * @...: further arguments to forward unmodified to @_call + * + * This function simplifies the implementation of macros. Whenever you + * implement a macro, provide the internal macro name as @_call and its + * argument as @_x1. Inside of your internal macro, you... + * + * - ...are safe against multiple evaluation errors, since C_CC_MACRO1 will + * store the initial parameters in temporary variables. + * + * - ...support constant folding, as C_CC_MACRO1 takes care to invoke your + * macro with the original values, if they are compile-time constant. + * + * - ...have unique variable names for recursive callers and will not run into + * variable-shadowing-warnings accidentally. + * + * - ...have properly typed arguments as C_CC_MACRO1 stores the original + * arguments in an `__auto_type` temporary variable. + * + * Return: Result of @_call is returned. + */ +#define C_CC_MACRO1(_call, _x1, ...) C_INTERNAL_CC_MACRO1(_call, __COUNTER__, (_x1), ## __VA_ARGS__) +#define C_INTERNAL_CC_MACRO1(_call, _x1q, _x1, ...) \ + __builtin_choose_expr( \ + __builtin_constant_p(_x1), \ + _call(_x1, ## __VA_ARGS__), \ + __extension__ ({ \ + const __auto_type C_VAR(X1, _x1q) = (_x1); \ + _call(C_VAR(X1, _x1q), ## __VA_ARGS__); \ + })) + +/** + * C_CC_MACRO2() - provide safe environment to a macro + * @_call: macro to call + * @_x1: first argument + * @_x2: second argument + * @...: further arguments to forward unmodified to @_call + * + * This is the 2-argument equivalent of C_CC_MACRO1(). + * + * Return: Result of @_call is returned. + */ +#define C_CC_MACRO2(_call, _x1, _x2, ...) C_INTERNAL_CC_MACRO2(_call, __COUNTER__, (_x1), __COUNTER__, (_x2), ## __VA_ARGS__) +#define C_INTERNAL_CC_MACRO2(_call, _x1q, _x1, _x2q, _x2, ...) \ + __builtin_choose_expr( \ + (__builtin_constant_p(_x1) && __builtin_constant_p(_x2)), \ + _call((_x1), (_x2), ## __VA_ARGS__), \ + __extension__ ({ \ + const __auto_type C_VAR(X1, _x1q) = (_x1); \ + const __auto_type C_VAR(X2, _x2q) = (_x2); \ + _call(C_VAR(X1, _x1q), C_VAR(X2, _x2q), ## __VA_ARGS__); \ + })) + +/** + * C_CC_MACRO3() - provide safe environment to a macro + * @_call: macro to call + * @_x1: first argument + * @_x2: second argument + * @_x3: third argument + * @...: further arguments to forward unmodified to @_call + * + * This is the 3-argument equivalent of C_CC_MACRO1(). + * + * Return: Result of @_call is returned. + */ +#define C_CC_MACRO3(_call, _x1, _x2, _x3, ...) C_INTERNAL_CC_MACRO3(_call, __COUNTER__, (_x1), __COUNTER__, (_x2), __COUNTER__, (_x3), ## __VA_ARGS__) +#define C_INTERNAL_CC_MACRO3(_call, _x1q, _x1, _x2q, _x2, _x3q, _x3, ...) \ + __builtin_choose_expr( \ + (__builtin_constant_p(_x1) && __builtin_constant_p(_x2) && __builtin_constant_p(_x3)), \ + _call((_x1), (_x2), (_x3), ## __VA_ARGS__), \ + __extension__ ({ \ + const __auto_type C_VAR(X1, _x1q) = (_x1); \ + const __auto_type C_VAR(X2, _x2q) = (_x2); \ + const __auto_type C_VAR(X3, _x3q) = (_x3); \ + _call(C_VAR(X1, _x1q), C_VAR(X2, _x2q), C_VAR(X3, _x3q), ## __VA_ARGS__); \ + })) + +/** + * C_ARRAY_SIZE() - calculate number of array elements at compile time + * @_x: array to calculate size of + * + * Return: Evaluates to a constant integer expression. + */ +#define C_ARRAY_SIZE(_x) \ + C_EXPR_ASSERT(sizeof(_x) / sizeof((_x)[0]), \ + /* \ + * Verify that `_x' is an array, not a pointer. Rely on \ + * `&_x[0]' degrading arrays to pointers. \ + */ \ + !__builtin_types_compatible_p( \ + __typeof__(_x), \ + __typeof__(&(*(__typeof__(_x)*)0)[0]) \ + ), \ + "C_ARRAY_SIZE() called with non-array argument" \ + ) + +/** + * C_DECIMAL_MAX() - calculate maximum length of the decimal + * representation of an integer + * @_type: integer variable/type + * + * This calculates the bytes required for the decimal representation of an + * integer of the given type. It accounts for a possible +/- prefix, but it + * does *NOT* include the trailing terminating zero byte. + * + * Return: Evaluates to a constant integer expression + */ +#define C_DECIMAL_MAX(_arg) \ + (_Generic((__typeof__(_arg)){ 0 }, \ + char: C_INTERNAL_DECIMAL_MAX(sizeof(char)), \ + signed char: C_INTERNAL_DECIMAL_MAX(sizeof(signed char)), \ + unsigned char: C_INTERNAL_DECIMAL_MAX(sizeof(unsigned char)), \ + signed short: C_INTERNAL_DECIMAL_MAX(sizeof(signed short)), \ + unsigned short: C_INTERNAL_DECIMAL_MAX(sizeof(unsigned short)), \ + signed int: C_INTERNAL_DECIMAL_MAX(sizeof(signed int)), \ + unsigned int: C_INTERNAL_DECIMAL_MAX(sizeof(unsigned int)), \ + signed long: C_INTERNAL_DECIMAL_MAX(sizeof(signed long)), \ + unsigned long: C_INTERNAL_DECIMAL_MAX(sizeof(unsigned long)), \ + signed long long: C_INTERNAL_DECIMAL_MAX(sizeof(signed long long)), \ + unsigned long long: C_INTERNAL_DECIMAL_MAX(sizeof(unsigned long long)))) +#define C_INTERNAL_DECIMAL_MAX(_bytes) \ + C_EXPR_ASSERT( \ + 1 + ((_bytes) <= 1 ? 3 : \ + (_bytes) <= 2 ? 5 : \ + (_bytes) <= 4 ? 10 : \ + 20), \ + (_bytes) <= 8, \ + "Invalid use of C_INTERNAL_DECIMAL_MAX()" \ + ) + +/** + * c_container_of() - cast a member of a structure out to the containing structure + * @_ptr: pointer to the member or NULL + * @_type: type of the container struct this is embedded in + * @_member: name of the member within the struct + * + * This uses `offsetof(3)` to turn a pointer to a structure-member into a + * pointer to the surrounding structure. + * + * Return: Pointer to the surrounding object. + */ +#define c_container_of(_ptr, _type, _member) C_CC_MACRO1(C_CONTAINER_OF, (_ptr), _type, _member) +#define C_CONTAINER_OF(_ptr, _type, _member) \ + __extension__ ({ \ + /* trigger warning if types do not match */ \ + (void)(&((_type *)0)->_member == (_ptr)); \ + _ptr ? (_type*)( (char*)_ptr - offsetof(_type, _member) ) : NULL; \ + }) + +/** + * c_max() - compute maximum of two values + * @_a: value A + * @_b: value B + * + * Calculate the maximum of both passed values. Both arguments are evaluated + * exactly once, under all circumstances. Furthermore, if both values are + * constant expressions, the result will be constant as well. + * + * The comparison of their values is performed with the types given by the + * caller. It is the caller's responsibility to convert them to suitable types + * if necessary. + * + * Return: Maximum of both values is returned. + */ +#define c_max(_a, _b) C_CC_MACRO2(C_MAX, (_a), (_b)) +#define C_MAX(_a, _b) ((_a) > (_b) ? (_a) : (_b)) + +/** + * c_min() - compute minimum of two values + * @_a: value A + * @_b: value B + * + * Calculate the minimum of both passed values. Both arguments are evaluated + * exactly once, under all circumstances. Furthermore, if both values are + * constant expressions, the result will be constant as well. + * + * The comparison of their values is performed with the types given by the + * caller. It is the caller's responsibility to convert them to suitable types + * if necessary. + * + * Return: Minimum of both values is returned. + */ +#define c_min(_a, _b) C_CC_MACRO2(C_MIN, (_a), (_b)) +#define C_MIN(_a, _b) ((_a) < (_b) ? (_a) : (_b)) + +/** + * c_less_by() - calculate clamped difference of two values + * @_a: minuend + * @_b: subtrahend + * + * Calculate [_a - _b], but clamp the result to 0. Both arguments are evaluated + * exactly once, under all circumstances. Furthermore, if both values are + * constant expressions, the result will be constant as well. + * + * The comparison of their values is performed with the types given by the + * caller. It is the caller's responsibility to convert them to suitable types + * if necessary. + * + * Return: This computes [_a - _b], if [_a > _b]. Otherwise, 0 is returned. + */ +#define c_less_by(_a, _b) C_CC_MACRO2(C_LESS_BY, (_a), (_b)) +#define C_LESS_BY(_a, _b) ((_a) > (_b) ? (_a) - (_b) : 0) + +/** + * c_clamp() - clamp value to lower and upper boundary + * @_x: value to clamp + * @_low: lower boundary + * @_high: higher boundary + * + * This clamps @_x to the lower and higher bounds given as @_low and @_high. + * All arguments are evaluated exactly once, and yield a constant expression if + * all arguments are constant as well. + * + * The comparison of their values is performed with the types given by the + * caller. It is the caller's responsibility to convert them to suitable types + * if necessary. + * + * Return: Clamped integer value. + */ +#define c_clamp(_x, _low, _high) C_CC_MACRO3(C_CLAMP, (_x), (_low), (_high)) +#define C_CLAMP(_x, _low, _high) ((_x) > (_high) ? (_high) : (_x) < (_low) ? (_low) : (_x)) + +/** + * c_div_round_up() - calculate integer quotient but round up + * @_x: dividend + * @_y: divisor + * + * Calculates [x / y] but rounds up the result to the next integer. All + * arguments are evaluated exactly once, and yield a constant expression if all + * arguments are constant. + * + * Note: + * [(x + y - 1) / y] suffers from an integer overflow, even though the + * computation should be possible in the given type. Therefore, we use + * [x / y + !!(x % y)]. Note that on most CPUs a division returns both the + * quotient and the remainder, so both should be equally fast. Furthermore, if + * the divisor is a power of two, the compiler will optimize it, anyway. + * + * The operationsare performed with the types given by the caller. It is the + * caller's responsibility to convert the arguments to suitable types if + * necessary. + * + * Return: The quotient is returned. + */ +#define c_div_round_up(_x, _y) C_CC_MACRO2(C_DIV_ROUND_UP, (_x), (_y)) +#define C_DIV_ROUND_UP(_x, _y) ((_x) / (_y) + !!((_x) % (_y))) + +/** + * c_align_to() - align value to a multiple + * @_val: value to align + * @_to: align to multiple of this + * + * This aligns @_val to a multiple of @_to. If @_val is already a multiple of + * @_to, @_val is returned unchanged. This function operates within the + * boundaries of the type of @_val and @_to. Make sure to cast them if needed. + * + * The arguments of this macro are evaluated exactly once. If both arguments + * are a constant expression, this also yields a constant return value. + * + * Note that @_to must be a power of 2, otherwise the behavior will not match + * expectations. + * + * Return: @_val aligned to a multiple of @_to + */ +#define c_align_to(_val, _to) C_CC_MACRO2(C_ALIGN_TO, (_val), (_to)) +#define C_ALIGN_TO(_val, _to) (((_val) + (_to) - 1) & ~((_to) - 1)) + +/** + * c_assert() - runtime assertions + * @expr_result: result of an expression + * + * This function behaves like the standard `assert(3)` macro. That is, if + * `NDEBUG` is defined, it is a no-op. In all other cases it will assert that + * the result of the passed expression is true. + * + * Unlike the standard `assert(3)` macro, this function always evaluates its + * argument. This means side-effects will always be evaluated! However, if the + * macro is used with constant expressions, the compiler will be able to + * optimize it away. + */ +#define c_assert(_x) ({ \ + const _c_unused_ bool c_assert_result = (_x); \ + assert(c_assert_result && #_x); \ + }) + +/** + * c_errno() - return valid errno + * + * This helper should be used to shut up gcc if you know 'errno' is valid (ie., + * errno is > 0). Instead of "return -errno;", use + * "return -c_errno();" It will suppress bogus gcc warnings in case it assumes + * 'errno' might be 0 (or <0) and thus the caller's error-handling might not be + * triggered. + * + * This helper should be avoided whenever possible. However, occasionally we + * really want to shut up gcc (especially with static/inline functions). In + * those cases, gcc usually cannot deduce that some error paths are guaranteed + * to be taken. Hence, making the return value explicit allows gcc to better + * optimize the code. + * + * Note that you really should never use this helper to work around broken libc + * calls or syscalls, not setting 'errno' correctly. + * + * Return: Positive error code is returned. + */ +static inline int c_errno(void) { + return _c_likely_(errno > 0) ? errno : ENOTRECOVERABLE; +} + +/* + * Common Destructors + * + * Followingly, there're a bunch of common 'static inline' destructors, which + * simply call the function that they're named after, but return "INVALID" + * instead of "void". This allows direct assignment to any member-field and/or + * variable they're defined in, like: + * + * foo = c_free(foo); + * + * or + * + * foo->bar = c_close(foo->bar); + * + * Furthermore, all those destructors can be safely called with the "INVALID" + * value as argument, and they will be a no-op. + */ + +static inline void *c_free(void *p) { + free(p); + return NULL; +} + +static inline int c_close(int fd) { + if (fd >= 0) + close(fd); + return -1; +} + +static inline FILE *c_fclose(FILE *f) { + if (f) + fclose(f); + return NULL; +} + +static inline DIR *c_closedir(DIR *d) { + if (d) + closedir(d); + return NULL; +} + +/* + * Common Cleanup Helpers + * + * A bunch of _c_cleanup_(foobarp) helpers that are used all over the place. + * Note that all of those have the "if (IS_INVALID(foobar))" check inline, so + * compilers can optimize most of the cleanup-paths in a function. However, if + * the function they call already does this _inline_, then it might be skipped. + */ + +#define C_DEFINE_CLEANUP(_type, _func) \ + static inline void _func ## p(_type *p) { \ + if (*p) \ + _func(*p); \ + } struct c_internal_trailing_semicolon + +#define C_DEFINE_DIRECT_CLEANUP(_type, _func) \ + static inline void _func ## p(_type *p) { \ + _func(*p); \ + } struct c_internal_trailing_semicolon + +static inline void c_freep(void *p) { + /* + * `foobar **` does not coerce to `void **`, so we need `void *` as + * argument type, and then we dereference manually. + */ + c_free(*(void **)p); +} + +C_DEFINE_DIRECT_CLEANUP(int, c_close); +C_DEFINE_CLEANUP(FILE *, c_fclose); +C_DEFINE_CLEANUP(DIR *, c_closedir); + +#ifdef __cplusplus +} +#endif |