prelude: Split bfs-specific utilities into new bfs.h header

1 files changed, 216 insertions, 0 deletions

diff --git a/src/bfs.h b/src/bfs.h
new file mode 100644
index 0000000..8820ab9
--- /dev/null
+++ b/src/bfs.h
@@ -0,0 +1,216 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+/**
+ * Configuration and fundamental utilities.
+ */
+
+#ifndef BFS_H
+#define BFS_H
+
+#include "prelude.h"
+
+// Standard versions
+
+/** Possible __STDC_VERSION__ values. */
+#define C95 199409L
+#define C99 199901L
+#define C11 201112L
+#define C17 201710L
+#define C23 202311L
+
+/** Possible _POSIX_C_SOURCE and _POSIX_<OPTION> values. */
+#define POSIX_1990 1
+#define POSIX_1992 2
+#define POSIX_1993 199309L
+#define POSIX_1995 199506L
+#define POSIX_2001 200112L
+#define POSIX_2008 200809L
+#define POSIX_2024 202405L
+
+// Build configuration
+
+#include "config.h"
+
+#ifndef BFS_COMMAND
+#  define BFS_COMMAND "bfs"
+#endif
+#ifndef BFS_HOMEPAGE
+#  define BFS_HOMEPAGE "https://tavianator.com/projects/bfs.html"
+#endif
+
+// This is a symbol instead of a literal so we don't have to rebuild everything
+// when the version number changes
+extern const char bfs_version[];
+
+extern const char bfs_confflags[];
+extern const char bfs_cc[];
+extern const char bfs_cppflags[];
+extern const char bfs_cflags[];
+extern const char bfs_ldflags[];
+extern const char bfs_ldlibs[];
+
+// Get __GLIBC__
+#include <assert.h>
+
+// Fundamental utilities
+
+/**
+ * Get the length of an array.
+ */
+#define countof(...) (sizeof(__VA_ARGS__) / sizeof(0[__VA_ARGS__]))
+
+/**
+ * False sharing/destructive interference/largest cache line size.
+ */
+#ifdef __GCC_DESTRUCTIVE_SIZE
+#  define FALSE_SHARING_SIZE __GCC_DESTRUCTIVE_SIZE
+#else
+#  define FALSE_SHARING_SIZE 64
+#endif
+
+/**
+ * True sharing/constructive interference/smallest cache line size.
+ */
+#ifdef __GCC_CONSTRUCTIVE_SIZE
+#  define TRUE_SHARING_SIZE __GCC_CONSTRUCTIVE_SIZE
+#else
+#  define TRUE_SHARING_SIZE 64
+#endif
+
+/**
+ * Alignment specifier that avoids false sharing.
+ */
+#define cache_align alignas(FALSE_SHARING_SIZE)
+
+// Wrappers for attributes
+
+/**
+ * Silence warnings about switch/case fall-throughs.
+ */
+#if __has_attribute(fallthrough)
+#  define _fallthrough __attribute__((fallthrough))
+#else
+#  define _fallthrough ((void)0)
+#endif
+
+/**
+ * Silence warnings about unused declarations.
+ */
+#if __has_attribute(unused)
+#  define _maybe_unused __attribute__((unused))
+#else
+#  define _maybe_unused
+#endif
+
+/**
+ * Warn if a value is unused.
+ */
+#if __has_attribute(warn_unused_result)
+#  define _nodiscard __attribute__((warn_unused_result))
+#else
+#  define _nodiscard
+#endif
+
+/**
+ * Hint to avoid inlining a function.
+ */
+#if __has_attribute(noinline)
+#  define _noinline __attribute__((noinline))
+#else
+#  define _noinline
+#endif
+
+/**
+ * Marks a non-returning function.
+ */
+#if __STDC_VERSION__ >= C23
+#  define _noreturn [[noreturn]]
+#else
+#  define _noreturn _Noreturn
+#endif
+
+/**
+ * Hint that a function is unlikely to be called.
+ */
+#if __has_attribute(cold)
+#  define _cold _noinline __attribute__((cold))
+#else
+#  define _cold _noinline
+#endif
+
+/**
+ * Adds compiler warnings for bad printf()-style function calls, if supported.
+ */
+#if __has_attribute(format)
+#  define _printf(fmt, args) __attribute__((format(printf, fmt, args)))
+#else
+#  define _printf(fmt, args)
+#endif
+
+/**
+ * Annotates functions that potentially modify and return format strings.
+ */
+#if __has_attribute(format_arg)
+#  define _format_arg(arg) __attribute__((format_arg(arg)))
+#else
+#  define _format_arg(arg)
+#endif
+
+/**
+ * Annotates allocator-like functions.
+ */
+#if __has_attribute(malloc)
+#  if __GNUC__ >= 11 && !__OPTIMIZE__ // malloc(deallocator) disables inlining on GCC
+#    define _malloc(...) _nodiscard __attribute__((malloc(__VA_ARGS__)))
+#  else
+#    define _malloc(...) _nodiscard __attribute__((malloc))
+#  endif
+#else
+#  define _malloc(...) _nodiscard
+#endif
+
+/**
+ * Specifies that a function returns allocations with a given alignment.
+ */
+#if __has_attribute(alloc_align)
+#  define _alloc_align(param) __attribute__((alloc_align(param)))
+#else
+#  define _alloc_align(param)
+#endif
+
+/**
+ * Specifies that a function returns allocations with a given size.
+ */
+#if __has_attribute(alloc_size)
+#  define _alloc_size(...) __attribute__((alloc_size(__VA_ARGS__)))
+#else
+#  define _alloc_size(...)
+#endif
+
+/**
+ * Shorthand for _alloc_align() and _alloc_size().
+ */
+#define _aligned_alloc(align, ...) _alloc_align(align) _alloc_size(__VA_ARGS__)
+
+/**
+ * Check if function multiversioning via GNU indirect functions (ifunc) is supported.
+ *
+ * Disabled on TSan due to https://github.com/google/sanitizers/issues/342.
+ */
+#ifndef BFS_USE_TARGET_CLONES
+#  if __has_attribute(target_clones) && (__GLIBC__ || __FreeBSD__) && !__SANITIZE_THREAD__
+#    define BFS_USE_TARGET_CLONES true
+#  endif
+#endif
+
+/**
+ * Apply the target_clones attribute, if available.
+ */
+#if BFS_USE_TARGET_CLONES
+#  define _target_clones(...) __attribute__((target_clones(__VA_ARGS__)))
+#else
+#  define _target_clones(...)
+#endif
+
+#endif // BFS_H