Add make script

3 files changed, 1109 insertions, 1 deletions

diff --git a/.gitignore b/.gitignore
index 5f62882..86c6e73 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,7 @@
 .cache/
-*.o
+*.[ao]
+*.so
 compile_commands.json
+make
 out
 test.c
diff --git a/cbs.h b/cbs.h
new file mode 100644
index 0000000..72ccef5
--- /dev/null
+++ b/cbs.h
@@ -0,0 +1,953 @@
+/* Single-header library to help write build scripts in C.  This library is
+   POSIX compliant, so it should work on all respectible UNIX-like systems.
+
+   You can find the CBS git repository at https://git.sr.ht/~mango/cbs and you
+   can include this in your project with the following command:
+
+       $ wget 'https://git.sr.ht/~mango/cbs/blob/master/cbs.h'
+
+   This library is licensed under the 0-Clause BSD license, and as such you may
+   do whatever you want to it, however you want to it, whenever you want.  You
+   are encouraged in fact to modify this library to suit your specific usecase.
+
+   All functions and macros are documented.  You can figure out the API pretty
+   easily by just reading the comments in this file.
+
+   In many cases you may want to be able to execute commands on multiple threads
+   to speed up compilation, such as the -j option when using Make.  Functions
+   for creating and using thread pools will be made available if the CBS_PTHREAD
+   macro is defined before including this file.  Do note that on POSIX platforms
+   it will require linking to the pthreads library when bootstrapping the build
+   script.
+
+   This file does not support C89.  Fuck C89, that shit is ancient.  Move on.
+
+   IMPORTANT NOTE: Any identifiers prefixed with an underscore (e.g. ‘_rebuild’)
+   are meant for internal use only and you should not touch them unless you know
+   what you’re doing.
+
+   IMPORTANT NOTE: All the functions and macros in this library will terminate
+   the program on error.  If this is undesired behavior, feel free to edit the
+   functions to return errors.
+
+   IMPORTANT NOTE: This library is built with the assumption that the source
+   file for your build script and your build script are in the SAME DIRECTORY.
+
+   There are a few exceptions to the above rule, and they are documented.
+
+   This library does not aim to ever support Windows */
+
+#ifndef C_BUILD_SYSTEM_H
+#define C_BUILD_SYSTEM_H
+
+#ifdef __GNUC__
+#	pragma GCC diagnostic push
+#	pragma GCC diagnostic ignored "-Wunused-function"
+#	pragma GCC diagnostic ignored "-Wparentheses"
+#endif
+
+/* Assert that the user is building for a supported platform.  The only portable
+   way to check for POSIX is to validate that unistd.h exists.  This is only
+   possible without compiler extensions in C23 (although some compilers support
+   it as an extension in earlier editions), so people compiling for pre-C23
+   might not get this error if on a bad platform, and may end up being a bit
+   confused.
+
+   It’s just a maybe though, this is nothing more than a sanity check for the
+   users sake. */
+#if defined(__has_include) && !__has_include(<unistd.h>)
+#	error "Non-POSIX platform detected"
+#endif
+
+#ifdef __APPLE__
+#	define st_mtim st_mtimespec
+#endif
+
+#include <sys/stat.h>
+#include <sys/wait.h>
+
+#include <errno.h>
+#include <libgen.h>
+#include <limits.h>
+#ifdef CBS_PTHREAD
+#	include <pthread.h>
+#endif
+#include <stdarg.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <wordexp.h>
+
+/* C23 changed a lot so we want to check for it */
+#if __STDC_VERSION__ >= 202000
+#	define CBS_IS_C23 1
+#endif
+
+/* Some C23 compat.  In C23 booleans are actual keywords, and the noreturn
+   attribute is different. */
+#if CBS_IS_C23
+#	define noreturn [[noreturn]]
+#else
+#	include <stdbool.h>
+#	include <stddef.h>
+#	include <stdnoreturn.h>
+#	define nullptr NULL
+#endif
+
+/* Give helpful diagnostics when people use die() incorrectly on GCC.  C23
+   introduced C++ attribute syntax, so we need a check for that too. */
+#ifdef __GNUC__
+#	if CBS_IS_C23
+#		define ATTR_FMT [[gnu::format(printf, 1, 2)]]
+#	else
+#		define ATTR_FMT __attribute__((format(printf, 1, 2)))
+#	endif
+#else
+#	define ATTR_FMT
+#endif
+
+/* Clang defines this attribute, and while it does nothing it does serve as
+   good documentation. */
+#ifndef _Nullable
+#	define _Nullable
+#endif
+
+/* Convert the given variadic arguments to a string array */
+#define _vtoa(...) ((char *[]){__VA_ARGS__})
+
+/* Internal global versions of argc and argv, so our functions and macros can
+   access them from anywhere. */
+static int _cbs_argc;
+static char **_cbs_argv;
+
+/* A vector of strings used to accumulate output of functions such as pcquery().
+   The array of strings buf has length len, and is not null-terminated.  You
+   should always zero-initialize variables of this type. */
+struct strv {
+	char **buf;
+	size_t len;
+};
+
+/* Free and zero a string vector.  Because this function zeros the structure, it
+   is safe to reuse the vector after this function is called. */
+static void strvfree(struct strv *);
+
+/* A wrapper function around realloc().  It behaves exactly the same except
+   instead of taking a buffer size as an argument, it takes a count n of
+   elements, and a size m of each element.  This allows it to properly check for
+   overflow, and errors if overflow would occur. */
+static void *bufalloc(void *_Nullable, size_t n, size_t m);
+
+/* Error reporting functions.  The die() function takes the same arguments as
+   printf() and prints the corresponding string to stderr.  It also prefixes the
+   string with the command name followed by a colon, and suffixes the string
+   with a colon and the error string returned from strerror().
+
+   If you want to print just the error message and no custom text, NULL may be
+   passed to die().  NULL should not be passed to diex().
+
+   diex() is the same as die() but does not print a strerror() error string. */
+ATTR_FMT noreturn static void die(const char *_Nullable, ...);
+ATTR_FMT noreturn static void diex(const char *, ...);
+
+/* Initializes some data required for this header to work properly.  This should
+   be the first thing called in main() with argc and argv passed.  It also
+   chdir()s into the directory where the build script is located. */
+static void cbsinit(int, char **);
+
+/* Get the number of items in the array a */
+#define lengthof(a) (sizeof(a) / sizeof(*(a)))
+
+/* Struct representing a CLI command that various functions act on.  You should
+   always zero-initialize variables of this type before use.
+
+   After executing a command, you can reuse the already allocated buffer this
+   command holds by calling cmdclr().  When you’re really done with an object of
+   this type, remember to call free() on ._argv.
+
+   The ._argv field is a NULL-terminated list of command arguments of length
+   ._len.  You may safely read from both of these fields but they should NOT be
+   modified without use of cmdadd() and cmdaddv(). */
+typedef struct {
+	char **_argv;
+	size_t _len, _cap;
+} cmd_t;
+
+/* Returns whether or not a binary of the given name exists in the users
+   environment as defined by $PATH. */
+static bool binexists(const char *);
+
+/* cmdadd() adds the variadic string arguments to the given command.
+   Alternatively, the cmdaddv() function adds the n strings pointed to by p to
+   the given command. */
+static void cmdaddv(cmd_t *, char **p, size_t n);
+#define cmdadd(cmd, ...) \
+	cmdaddv(cmd, _vtoa(__VA_ARGS__), lengthof(_vtoa(__VA_ARGS__)))
+
+/* Clear (but not free) the command c.  Useful for reusing the same command
+   struct to minimize allocations. */
+static void cmdclr(cmd_t *c);
+
+/* The cmdexec() function executes the given command and waits for it to
+   terminate, returning its exit code.  The cmdexeca() function executes the
+   given command and returns immediately, returning its process ID.
+
+   The cmdexecb() function is like cmdexec() except it writes the given commands
+   standard output to the character buffer pointed to by p.  It also stores the
+   size of the output in *n.  The character buffer p is null-terminated.  If the
+   given command produces no output to the standard output, p will be set to
+   NULL.
+
+   cmdexec() and cmdexecb() have the same return values as cmdwait(). */
+static int cmdexec(cmd_t);
+static pid_t cmdexeca(cmd_t);
+static int cmdexecb(cmd_t, char **p, size_t *n);
+
+/* Wait for the process with the given PID to terminate, and return its exit
+   status.  If the process was terminated by a signal 256 is returned. */
+static int cmdwait(pid_t);
+
+/* Write a representation of the given command to the given file stream.  This
+   can be used to mimick the echoing behavior of make(1).  The cmdput() function
+   is a nice convenience function so you can avoid writing ‘stdout’ all the
+   time. */
+static void cmdput(cmd_t);
+static void cmdputf(FILE *, cmd_t);
+
+/* Expand the environment variable s using /bin/sh expansion rules and append
+   the results in the given string vector.  If the environment variable is NULL
+   or empty, then store the strings specified by the array p of length n.
+
+   env_or_default() is the same as env_or_defaultv() but you provide p as
+   variadic arguments.
+
+   If the pointer p is null, then no default value is appended to the given
+   string vector when the environment variable is not present. */
+static void env_or_defaultv(struct strv *, const char *s, char *_Nullable *p,
+                            size_t n);
+#define env_or_default(sv, s, ...) \
+	env_or_defaultv((sv), (s), _vtoa(__VA_ARGS__), lengthof(_vtoa(__VA_ARGS__)))
+
+/* Returns if a file exists at the given path.  A return value of false may also
+   mean you don’t have the proper file access permissions, which will also set
+   errno. */
+static bool fexists(const char *);
+
+/* Compare the modification dates of the two named files.
+
+   A return value >0 means the LHS is newer than the RHS.
+   A return value <0 means the LHS is older than the RHS.
+   A return value of 0 means the LHS and RHS have the same modification date.
+
+   The fmdnewer() and fmdolder() functions are wrappers around fmdcmp() that
+   return true when the LHS is newer or older than the RHS respectively. */
+static int fmdcmp(const char *, const char *);
+static bool fmdolder(const char *, const char *);
+static bool fmdnewer(const char *, const char *);
+
+/* Report if any of n files specified by p render the file base outdated.  If
+   the file base does not exist, this function returns true.  You will typically
+   call this with a compiled program as base, and C source files as p.  The
+   macro foutdated() is a wrapper around foutdatedv() that allows you to specify
+   the sources to base as variadic arguments instead of as an array. */
+static bool foutdatedv(const char *base, const char **p, size_t n);
+#define foutdated(s, ...) \
+	foutdatedv(s, (const char **)_vtoa(__VA_ARGS__), \
+	           lengthof(_vtoa(__VA_ARGS__)))
+
+/* Rebuild the build script if it has been modified, and execute the newly built
+   script.  You should call the rebuild() macro at the very beginning of main(),
+   but right after cbsinit().  You probably don’t want to call _rebuild()
+   directly.
+
+   NOTE: This function/macro REQUIRES that the source for the build script and
+   the compiled build script are in the SAME DIRECTORY. */
+static void _rebuild(char *);
+#define rebuild() _rebuild(__FILE__)
+
+/* Get the number of available CPUs, or -1 on error.  This function also returns
+   -1 if the _SC_NPROCESSORS_ONLN flag to sysconf(3) is not available.  In that
+   case, errno will not be set. */
+static int nproc(void);
+
+/* Append the arguments returned by an invokation of pkg-config for the library
+   lib to the given string vector.  The flags argument is one-or-more of the
+   flags in the pkg_config_flags enum bitwise-ORed together.
+
+   If PKGC_CFLAGS is specified, call pkg-config with ‘--cflags’.
+   If PKGC_LIBS is specified, call pkg-config with ‘--libs’.
+
+   This function returns true on success and false if pkg-config is not found on
+   the system.  To check for pkg-configs existance, you can use the binexists()
+   function. */
+static bool pcquery(struct strv *, char *lib, int flags);
+enum pkg_config_flags {
+	PKGC_LIBS = 1 << 0,
+	PKGC_CFLAGS = 1 << 1,
+};
+
+#ifdef CBS_PTHREAD
+
+/* A tfunc_t represents a function to be executed by a threads in a thread pool.
+   It takes an argument in the form of a void * and returns nothing. */
+typedef void (*tfunc_t)(void *);
+
+/* A tfunc_free_t represents a function which frees the argument passed to a
+   tfunc_t function. */
+typedef void (*tfree_func_t)(void *);
+
+/* A thread pool job queue.  Meant for internal-use only. */
+struct _tjob {
+	void *arg;
+	tfunc_t fn;
+	tfree_func_t free;
+	struct _tjob *next;
+};
+
+/* A basic thread pool.  None of its fields should really be touched. */
+typedef struct {
+	bool _stop;
+	size_t _tcnt, _left;
+	pthread_t *_thrds;
+	pthread_cond_t _cnd;
+	pthread_mutex_t _mtx;
+	struct _tjob *_head, *_tail;
+} tpool_t;
+
+/* Initialize and destroy a thread pool.  The tpinit() function initializes the
+   given thread pool and creates n threads ready to execute work.  The tpfree()
+   function should be called after a thread pool has been used to release all
+   resources used by the thread pool. */
+static void tpinit(tpool_t *, size_t n);
+static void tpfree(tpool_t *);
+
+/* Wait for all jobs on the given thread pool to be executed.  Note that this
+   function does not destroy the threads or free any resources — those are tasks
+   for the tpfree() function. */
+static void tpwait(tpool_t *);
+
+/* Enqueue and dequeue jobs to the thread pools job queue.  The tpenq() function
+   is threadsafe while the _tpdeq() function is not (so don’t use it).  When
+   calling the tpenq() function, the function fn will be queued to be executed
+   by a thread in the thread pool with the argument arg.  If the given argument
+   needs to be deallocated after the job completes, you can pass the free
+   argument which will be called with the given argument after use.  If free is
+   NULL, it will be ignored.
+
+   The free() function is a valid argument to the free parameter. */
+static void tpenq(tpool_t *, tfunc_t fn, void *arg,
+                  tfree_func_t _Nullable free);
+static struct _tjob *_tpdeq(tpool_t *);
+
+#endif /* CBS_PTHREAD */
+
+/* BEGIN DEFINITIONS */
+
+void
+strvfree(struct strv *v)
+{
+	free(v->buf);
+	memset(v, 0, sizeof(*v));
+}
+
+void *
+bufalloc(void *p, size_t n, size_t m)
+{
+	if (n && SIZE_MAX / n < m) {
+		errno = EOVERFLOW;
+		die(__func__);
+	}
+
+	if (!(p = realloc(p, n * m)))
+		die(__func__);
+	return p;
+}
+
+void
+die(const char *fmt, ...)
+{
+	int e = errno;
+	va_list ap;
+
+	va_start(ap, fmt);
+	flockfile(stderr);
+	fprintf(stderr, "%s: ", *_cbs_argv);
+	if (fmt) {
+		vfprintf(stderr, fmt, ap);
+		fprintf(stderr, ": ");
+	}
+	fprintf(stderr, "%s\n", strerror(e));
+	exit(EXIT_FAILURE);
+}
+
+void
+diex(const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	flockfile(stderr);
+	fprintf(stderr, "%s: ", *_cbs_argv);
+	vfprintf(stderr, fmt, ap);
+	fputc('\n', stderr);
+	exit(EXIT_FAILURE);
+}
+
+void
+cbsinit(int argc, char **argv)
+{
+	char *s;
+
+	_cbs_argc = argc;
+	_cbs_argv = bufalloc(nullptr, argc, sizeof(char *));
+	for (int i = 0; i < argc; i++) {
+		if (!(_cbs_argv[i] = strdup(argv[i]))) {
+			/* We might not have set _cbs_argv[0] yet, so we can’t use die() */
+			fprintf(stderr, "%s: strdup: %s\n", *argv, strerror(errno));
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	/* Cd to dirname(argv[0]).  We can’t use dirname(3) because it may modify
+	   the source string. */
+	if (s = strrchr(_cbs_argv[0], '/')) {
+		s[0] = '\0';
+		if (chdir(_cbs_argv[0]) == -1)
+			die("chdir: %s", s);
+		s[0] = '/';
+	}
+}
+
+static size_t
+_next_powerof2(size_t x)
+{
+#if defined(__has_builtin) && __has_builtin(__builtin_clzl)
+	x = x <= 1 ? 1 : 1 << (64 - __builtin_clzl(x - 1));
+#else
+	if (x) {
+		x--;
+		x |= x >> 1;
+		x |= x >> 2;
+		x |= x >> 4;
+		x |= x >> 8;
+		if (sizeof(size_t) >= 4)
+			x |= x >> 16;
+		if (sizeof(size_t) >= 8)
+			x |= x >> 32;
+	}
+	x++;
+#endif
+
+	return x;
+}
+
+bool
+binexists(const char *name)
+{
+	char *p, *path;
+
+	if (!(path = getenv("PATH")))
+		diex("PATH environment variable not found");
+
+	if (!(path = strdup(path)))
+		die("strdup");
+	p = strtok(path, ":");
+	while (p) {
+		char buf[PATH_MAX];
+		snprintf(buf, sizeof(buf), "%s/%s", p, name);
+		if (fexists(buf)) {
+			free(path);
+			return true;
+		}
+
+		p = strtok(nullptr, ":");
+	}
+
+	free(path);
+	return false;
+}
+
+void
+cmdaddv(cmd_t *cmd, char **xs, size_t n)
+{
+	if (cmd->_len + n >= cmd->_cap) {
+		cmd->_cap = _next_powerof2(cmd->_len + n) + 2;
+		cmd->_argv = bufalloc(cmd->_argv, cmd->_cap, sizeof(char *));
+	}
+
+	memcpy(cmd->_argv + cmd->_len, xs, n * sizeof(*xs));
+	cmd->_len += n;
+	cmd->_argv[cmd->_len] = nullptr;
+}
+
+void
+cmdclr(cmd_t *c)
+{
+	c->_len = 0;
+	*c->_argv = nullptr;
+}
+
+int
+cmdexec(cmd_t c)
+{
+	return cmdwait(cmdexeca(c));
+}
+
+pid_t
+cmdexeca(cmd_t c)
+{
+	pid_t pid;
+
+	switch (pid = fork()) {
+	case -1:
+		die("fork");
+	case 0:
+		execvp(*c._argv, c._argv);
+		die("execvp: %s", *c._argv);
+	}
+
+	return pid;
+}
+
+int
+cmdexecb(cmd_t c, char **p, size_t *n)
+{
+	enum {
+		FD_R,
+		FD_W,
+	};
+	pid_t pid;
+	int fds[2];
+	char *buf;
+	size_t len, blksize;
+	struct stat sb;
+
+	if (pipe(fds) == -1)
+		die("pipe");
+
+	switch (pid = fork()) {
+	case -1:
+		die("fork");
+	case 0:
+		close(fds[FD_R]);
+		if (dup2(fds[FD_W], STDOUT_FILENO) == -1)
+			die("dup2");
+		execvp(*c._argv, c._argv);
+		die("execvp: %s", *c._argv);
+	}
+
+	close(fds[FD_W]);
+
+	buf = nullptr;
+	len = 0;
+
+	blksize = fstat(fds[FD_R], &sb) == -1 ? BUFSIZ : sb.st_blksize;
+	for (;;) {
+		/* This can maybe somewhere somehow break some system.  I do not care */
+		char tmp[blksize];
+		ssize_t nr;
+
+		if ((nr = read(fds[FD_R], tmp, blksize)) == -1)
+			die("read");
+		if (!nr)
+			break;
+		buf = bufalloc(buf, len + nr + 1, sizeof(char));
+		memcpy(buf + len, tmp, nr);
+		len += nr;
+	}
+
+	close(fds[FD_R]);
+	if (buf)
+		buf[len] = 0;
+	*p = buf;
+	*n = len;
+	return cmdwait(pid);
+}
+
+int
+cmdwait(pid_t pid)
+{
+	for (;;) {
+		int ws;
+		if (waitpid(pid, &ws, 0) == -1)
+			die("waitpid");
+
+		if (WIFEXITED(ws))
+			return WEXITSTATUS(ws);
+
+		if (WIFSIGNALED(ws))
+			return 256;
+	}
+}
+
+/* import shlex
+
+   s = '#define SHELL_SAFE "'
+   for c in map(chr, range(128)):
+       if not shlex._find_unsafe(c):
+           s += c
+   print(s + '"') */
+#define SHELL_SAFE \
+	"%+,-./0123456789:=@ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz"
+
+void
+cmdput(cmd_t c)
+{
+	cmdputf(stdout, c);
+}
+
+void
+cmdputf(FILE *stream, cmd_t cmd)
+{
+	flockfile(stream);
+	for (size_t i = 0; i < cmd._len; i++) {
+		bool safe = true;
+		char *p, *q;
+
+		p = q = cmd._argv[i];
+		for (; *q; q++) {
+			if (!strchr(SHELL_SAFE, *q)) {
+				safe = false;
+				break;
+			}
+		}
+
+		if (safe)
+			fputs(p, stream);
+		else {
+			putc('\'', stream);
+			for (q = p; *q; q++) {
+				if (*q == '\'')
+					fputs("'\"'\"'", stream);
+				else
+					putc(*q, stream);
+			}
+			putc('\'', stream);
+		}
+
+		putc(i == cmd._len - 1 ? '\n' : ' ', stream);
+	}
+	funlockfile(stream);
+}
+
+void
+env_or_defaultv(struct strv *sv, const char *s, char **p, size_t n)
+{
+	wordexp_t we;
+	const char *ev;
+
+	if ((ev = getenv(s)) && *ev) {
+		switch (wordexp(ev, &we, WRDE_NOCMD)) {
+		case WRDE_BADCHAR:
+		case WRDE_BADVAL:
+		case WRDE_SYNTAX:
+			errno = EINVAL;
+			die("wordexp");
+		case WRDE_NOSPACE:
+			errno = ENOMEM;
+			die("wordexp");
+		}
+
+		p = we.we_wordv;
+		n = we.we_wordc;
+	} else if (!n || !*p)
+		return;
+
+	sv->buf = bufalloc(sv->buf, sv->len + n, sizeof(*sv->buf));
+	for (size_t i = 0; i < n; i++) {
+		if (!(sv->buf[sv->len + i] = strdup(p[i])))
+			die("strdup");
+	}
+	sv->len += n;
+
+	if (ev && *ev)
+		wordfree(&we);
+}
+
+bool
+fexists(const char *f)
+{
+	return !access(f, F_OK);
+}
+
+int
+fmdcmp(const char *lhs, const char *rhs)
+{
+	struct stat sbl, sbr;
+
+	if (stat(lhs, &sbl) == -1)
+		die("%s", lhs);
+	if (stat(rhs, &sbr) == -1)
+		die("%s", rhs);
+
+	return sbl.st_mtim.tv_sec == sbr.st_mtim.tv_sec
+	         ? sbl.st_mtim.tv_nsec - sbr.st_mtim.tv_nsec
+	         : sbl.st_mtim.tv_sec - sbr.st_mtim.tv_sec;
+}
+
+bool
+fmdnewer(const char *lhs, const char *rhs)
+{
+	return fmdcmp(lhs, rhs) > 0;
+}
+
+bool
+fmdolder(const char *lhs, const char *rhs)
+{
+	return fmdcmp(lhs, rhs) < 0;
+}
+
+bool
+foutdatedv(const char *src, const char **deps, size_t n)
+{
+	if (!fexists(src))
+		return true;
+	for (size_t i = 0; i < n; i++) {
+		if (fmdolder(src, deps[i]))
+			return true;
+	}
+	return false;
+}
+
+void
+_rebuild(char *src)
+{
+	char *bbn, *sbn, *argv0;
+	cmd_t cmd = {0};
+	size_t bufsiz;
+
+	/* We assume that the compiled binary and the source file are in the same
+	   directory. */
+	if (sbn = strrchr(src, '/'))
+		sbn++;
+	else
+		sbn = src;
+	if (bbn = strrchr(*_cbs_argv, '/'))
+		bbn++;
+	else
+		bbn = src;
+
+	if (!foutdated(bbn, sbn))
+		return;
+
+	cmdadd(&cmd, "cc");
+#ifdef CBS_PTHREAD
+	cmdadd(&cmd, "-lpthread");
+#endif
+	cmdadd(&cmd, "-o", bbn, sbn);
+	cmdput(cmd);
+	if (cmdexec(cmd))
+		diex("Compilation of build script failed");
+
+	cmdclr(&cmd);
+
+	argv0 = bufalloc(nullptr, strlen(bbn) + 3, 1);
+	*_cbs_argv = argv0;
+
+	*argv0++ = '.';
+	*argv0++ = '/';
+	strcpy(argv0, bbn);
+
+	cmdaddv(&cmd, _cbs_argv, _cbs_argc);
+	execvp(*cmd._argv, cmd._argv);
+	die("execvp: %s", *cmd._argv);
+}
+
+int
+nproc(void)
+{
+#ifdef _SC_NPROCESSORS_ONLN
+	return (int)sysconf(_SC_NPROCESSORS_ONLN);
+#else
+	errno = 0;
+	return -1;
+#endif
+}
+
+bool
+pcquery(struct strv *vec, char *lib, int flags)
+{
+	int ec;
+	char *p;
+	size_t n;
+	cmd_t c = {0};
+	wordexp_t we;
+
+	p = nullptr;
+
+	cmdadd(&c, "pkg-config");
+	if (flags & PKGC_LIBS)
+		cmdadd(&c, "--libs");
+	if (flags & PKGC_CFLAGS)
+		cmdadd(&c, "--cflags");
+	cmdadd(&c, lib);
+
+	if ((ec = cmdexecb(c, &p, &n))) {
+		if (errno == ENOENT) {
+			free(c._argv);
+			return false;
+		}
+		diex("pkg-config terminated with exit-code %d", ec);
+	}
+
+	if (!p)
+		return true;
+
+	/* Remove trailing newline */
+	p[n - 1] = 0;
+
+	switch (wordexp(p, &we, WRDE_NOCMD)) {
+	case WRDE_BADCHAR:
+	case WRDE_BADVAL:
+	case WRDE_SYNTAX:
+		errno = EINVAL;
+		die("wordexp");
+	case WRDE_NOSPACE:
+		errno = ENOMEM;
+		die("wordexp");
+	}
+
+	vec->buf = bufalloc(vec->buf, vec->len + we.we_wordc, sizeof(char *));
+	for (size_t i = 0; i < we.we_wordc; i++) {
+		char *p = strdup(we.we_wordv[i]);
+		if (!p)
+			die(__func__);
+		vec->buf[vec->len++] = p;
+	}
+
+	wordfree(&we);
+	free(p);
+	return true;
+}
+
+#ifdef CBS_PTHREAD
+
+static void *
+_tpwork(void *arg)
+{
+	tpool_t *tp = arg;
+
+	while (!tp->_stop) {
+		struct _tjob *j;
+
+		pthread_mutex_lock(&tp->_mtx);
+		while (!tp->_stop && !tp->_head)
+			pthread_cond_wait(&tp->_cnd, &tp->_mtx);
+		if (tp->_stop) {
+			pthread_mutex_unlock(&tp->_mtx);
+			break;
+		}
+
+		j = _tpdeq(tp);
+		pthread_mutex_unlock(&tp->_mtx);
+
+		j->fn(j->arg);
+		if (j->free)
+			j->free(j->arg);
+		free(j);
+
+		pthread_mutex_lock(&tp->_mtx);
+		tp->_left--;
+		pthread_cond_broadcast(&tp->_cnd);
+		pthread_mutex_unlock(&tp->_mtx);
+	}
+
+	return nullptr;
+}
+
+void
+tpinit(tpool_t *tp, size_t n)
+{
+	tp->_tcnt = n;
+	tp->_stop = false;
+	tp->_left = 0;
+	tp->_head = tp->_tail = nullptr;
+	tp->_thrds = bufalloc(nullptr, n, sizeof(pthread_t));
+	pthread_cond_init(&tp->_cnd, nullptr);
+	pthread_mutex_init(&tp->_mtx, nullptr);
+
+	for (size_t i = 0; i < n; i++)
+		pthread_create(tp->_thrds + i, nullptr, _tpwork, tp);
+}
+
+void
+tpfree(tpool_t *tp)
+{
+	tp->_stop = true;
+
+	pthread_mutex_lock(&tp->_mtx);
+	pthread_cond_broadcast(&tp->_cnd);
+	pthread_mutex_unlock(&tp->_mtx);
+
+	for (size_t i = 0; i < tp->_tcnt; i++)
+		pthread_join(tp->_thrds[i], nullptr);
+
+	free(tp->_thrds);
+	while (tp->_head) {
+		struct _tjob *j = _tpdeq(tp);
+		if (j->free)
+			j->free(j->arg);
+		free(j);
+	}
+
+	pthread_cond_destroy(&tp->_cnd);
+	pthread_mutex_destroy(&tp->_mtx);
+}
+
+struct _tjob *
+_tpdeq(tpool_t *tp)
+{
+	struct _tjob *j = tp->_head;
+
+	if (j) {
+		tp->_head = tp->_head->next;
+		if (!tp->_head)
+			tp->_tail = nullptr;
+	}
+
+	return j;
+}
+
+void
+tpenq(tpool_t *tp, tfunc_t fn, void *arg, tfree_func_t free)
+{
+	struct _tjob *j = bufalloc(nullptr, 1, sizeof(struct _tjob));
+	*j = (struct _tjob){
+		.fn = fn,
+		.arg = arg,
+		.free = free,
+	};
+
+	pthread_mutex_lock(&tp->_mtx);
+	if (tp->_tail)
+		tp->_tail->next = j;
+	if (!tp->_head)
+		tp->_head = j;
+	tp->_tail = j;
+	tp->_left++;
+	pthread_cond_signal(&tp->_cnd);
+	pthread_mutex_unlock(&tp->_mtx);
+}
+
+void
+tpwait(tpool_t *tp)
+{
+	pthread_mutex_lock(&tp->_mtx);
+	while (!tp->_stop && tp->_left)
+		pthread_cond_wait(&tp->_cnd, &tp->_mtx);
+	pthread_mutex_unlock(&tp->_mtx);
+}
+
+#endif /* CBS_PTHREAD */
+
+#ifdef __GNUC__
+#	pragma GCC diagnostic pop
+#endif
+
+#ifdef __APPLE__
+#	undef st_mtim
+#endif
+
+#endif /* !C_BUILD_SYSTEM_H */
diff --git a/make.c b/make.c
new file mode 100644
index 0000000..3be57c2
--- /dev/null
+++ b/make.c
@@ -0,0 +1,153 @@
+#define _GNU_SOURCE
+#include <errno.h>
+#include <glob.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define CBS_PTHREAD
+#include "cbs.h"
+
+#define CC         "gcc"
+#define CFLAGS_ALL WARNINGS, "-pipe", "-std=c23", "-Iinclude"
+#define CFLAGS_DBG CFLAGS_ALL, "-g", "-ggdb3", "-Og"
+#ifdef __APPLE__
+#	define CFLAGS_RLS CFLAGS_ALL, "-O3", "-flto"
+#else
+#	define CFLAGS_RLS \
+		CFLAGS_ALL, "-O3", "-flto", "-march=native", "-mtune=native"
+#endif
+#define LIBNAME "libmlib"
+#define WARNINGS \
+	"-Wall", "-Wextra", "-Wpedantic", "-Werror", "-Wno-attributes", \
+		"-Wno-pointer-sign"
+
+#define CMDPRC(c) \
+	do { \
+		int ec; \
+		cmdput(c); \
+		if ((ec = cmdexec(c)) != EXIT_SUCCESS) \
+			diex("%s terminated with exit-code %d", *(c)._argv, ec); \
+		cmdclr(&(c)); \
+	} while (false)
+
+#define flagset(o)  (flags & (1 << ((o) - 'a')))
+#define streq(x, y) (!strcmp(x, y))
+
+static int globerr(const char *, int);
+static void work(void *);
+
+static unsigned long flags;
+
+int
+main(int argc, char **argv)
+{
+	int opt, procs = -1;
+
+	cbsinit(argc, argv);
+	rebuild();
+
+	while ((opt = getopt(argc, argv, "fj:r")) != -1) {
+		switch (opt) {
+		case '?':
+			fprintf(stderr, "Usage: %s [-j procs] [-fr]\n", *argv);
+			exit(EXIT_FAILURE);
+		case 'j':
+			procs = atoi(optarg);
+			break;
+		default:
+			flags |= 1 << (opt - 'a');
+		}
+	}
+
+	argc -= optind;
+	argv += optind;
+
+	if (argc >= 1) {
+		if (!streq(*argv, "clean")) {
+			diex("invalid subcommand — ‘%s’", *argv);
+			exit(EXIT_FAILURE);
+		}
+		cmd_t c = {};
+		cmdadd(&c, "find", ".", "(", "-name", "*.[ao]", "-or", "-name", "*.so",
+		       ")", "-delete");
+		CMDPRC(c);
+	} else {
+		cmd_t c = {};
+		glob_t g;
+		tpool_t tp;
+
+		if (glob("lib/*/*.c", 0, globerr, &g))
+			die("glob");
+
+		if (procs == -1 && (procs = nproc()) == -1) {
+			if (errno)
+				die("nproc");
+			procs = 8;
+		}
+
+		tpinit(&tp, procs);
+		for (size_t i = 0; i < g.gl_pathc; i++)
+			tpenq(&tp, work, g.gl_pathv[i], nullptr);
+		tpwait(&tp);
+		tpfree(&tp);
+
+		for (size_t i = 0; i < g.gl_pathc; i++)
+			g.gl_pathv[i][strlen(g.gl_pathv[i]) - 1] = 'o';
+
+		if (flagset('f')
+		    || foutdatedv(LIBNAME ".a", (const char **)g.gl_pathv, g.gl_pathc))
+		{
+			cmdadd(&c, "ar", "rcs", LIBNAME ".a");
+			cmdaddv(&c, g.gl_pathv, g.gl_pathc);
+			CMDPRC(c);
+		}
+
+		if (flagset('f')
+		    || foutdatedv(LIBNAME ".so", (const char **)g.gl_pathv, g.gl_pathc))
+		{
+			struct strv sv = {};
+			env_or_default(&sv, "CC", CC);
+			cmdaddv(&c, sv.buf, sv.len);
+			cmdadd(&c, "-shared", "-o", LIBNAME ".so");
+			cmdaddv(&c, g.gl_pathv, g.gl_pathc);
+			CMDPRC(c);
+		}
+
+		globfree(&g);
+	}
+
+	return EXIT_SUCCESS;
+}
+
+void
+work(void *p)
+{
+	char *dst, *src = p;
+	cmd_t c = {};
+	struct strv sv = {};
+
+	if (!(dst = strdup(src)))
+		die("strdup");
+	dst[strlen(dst) - 1] = 'o';
+
+	if (flagset('f') || foutdated(dst, src)) {
+		env_or_default(&sv, "CC", CC);
+		if (flagset('r'))
+			env_or_default(&sv, "CFLAGS", CFLAGS_RLS);
+		else
+			env_or_default(&sv, "CFLAGS", CFLAGS_DBG);
+		cmdaddv(&c, sv.buf, sv.len);
+		cmdadd(&c, "-Iinclude", "-fPIC", "-o", dst, "-c", src);
+		CMDPRC(c);
+	}
+
+	free(dst);
+}
+
+int
+globerr(const char *s, int e)
+{
+	errno = e;
+	die("glob: %s", s);
+}