chg: add fchdirx as a utility function

As part of the series to support long socket paths, we need to use fchdir and
check its result in several places. Make it a utility function.

contrib/chg/util.c

@@ -1,173 +1,180 b''
 /*
  * Utility functions
  *
  * Copyright (c) 2011 Yuya Nishihara <[e-mail]>
  *
  * This software may be used and distributed according to the terms of the
  * GNU General Public License version 2 or any later version.
  */
 
 #include <errno.h>
 #include <signal.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
 #include "util.h"
 
 static int colorenabled = 0;
 
 static inline void fsetcolor(FILE *fp, const char *code)
 {
 	if (!colorenabled)
 		return;
 	fprintf(fp, "\033[%sm", code);
 }
 
 static void vabortmsgerrno(int no, const char *fmt, va_list args)
 {
 	fsetcolor(stderr, "1;31");
 	fputs("chg: abort: ", stderr);
 	vfprintf(stderr, fmt, args);
 	if (no != 0)
 		fprintf(stderr, " (errno = %d, %s)", no, strerror(no));
 	fsetcolor(stderr, "");
 	fputc('\n', stderr);
 	exit(255);
 }
 
 void abortmsg(const char *fmt, ...)
 {
 	va_list args;
 	va_start(args, fmt);
 	vabortmsgerrno(0, fmt, args);
 	va_end(args);
 }
 
 void abortmsgerrno(const char *fmt, ...)
 {
 	int no = errno;
 	va_list args;
 	va_start(args, fmt);
 	vabortmsgerrno(no, fmt, args);
 	va_end(args);
 }
 
 static int debugmsgenabled = 0;
 
 void enablecolor(void)
 {
 	colorenabled = 1;
 }
 
 void enabledebugmsg(void)
 {
 	debugmsgenabled = 1;
 }
 
 void debugmsg(const char *fmt, ...)
 {
 	if (!debugmsgenabled)
 		return;
 
 	va_list args;
 	va_start(args, fmt);
 	fsetcolor(stderr, "1;30");
 	fputs("chg: debug: ", stderr);
 	vfprintf(stderr, fmt, args);
 	fsetcolor(stderr, "");
 	fputc('\n', stderr);
 	va_end(args);
 }
 
+void fchdirx(int dirfd)
+{
+	int r = fchdir(dirfd);
+	if (r == -1)
+		abortmsgerrno("failed to fchdir");
+}
+
 void *mallocx(size_t size)
 {
 	void *result = malloc(size);
 	if (!result)
 		abortmsg("failed to malloc");
 	return result;
 }
 
 void *reallocx(void *ptr, size_t size)
 {
 	void *result = realloc(ptr, size);
 	if (!result)
 		abortmsg("failed to realloc");
 	return result;
 }
 
 /*
  * Execute a shell command in mostly the same manner as system(), with the
  * give environment variables, after chdir to the given cwd. Returns a status
  * code compatible with the Python subprocess module.
  */
 int runshellcmd(const char *cmd, const char *envp[], const char *cwd)
 {
 	enum { F_SIGINT = 1, F_SIGQUIT = 2, F_SIGMASK = 4, F_WAITPID = 8 };
 	unsigned int doneflags = 0;
 	int status = 0;
 	struct sigaction newsa, oldsaint, oldsaquit;
 	sigset_t oldmask;
 
 	/* block or mask signals just as system() does */
 	memset(&newsa, 0, sizeof(newsa));
 	newsa.sa_handler = SIG_IGN;
 	newsa.sa_flags = 0;
 	if (sigemptyset(&newsa.sa_mask) < 0)
 		goto done;
 	if (sigaction(SIGINT, &newsa, &oldsaint) < 0)
 		goto done;
 	doneflags |= F_SIGINT;
 	if (sigaction(SIGQUIT, &newsa, &oldsaquit) < 0)
 		goto done;
 	doneflags |= F_SIGQUIT;
 
 	if (sigaddset(&newsa.sa_mask, SIGCHLD) < 0)
 		goto done;
 	if (sigprocmask(SIG_BLOCK, &newsa.sa_mask, &oldmask) < 0)
 		goto done;
 	doneflags |= F_SIGMASK;
 
 	pid_t pid = fork();
 	if (pid < 0)
 		goto done;
 	if (pid == 0) {
 		sigaction(SIGINT, &oldsaint, NULL);
 		sigaction(SIGQUIT, &oldsaquit, NULL);
 		sigprocmask(SIG_SETMASK, &oldmask, NULL);
 		if (cwd && chdir(cwd) < 0)
 			_exit(127);
 		const char *argv[] = {"sh", "-c", cmd, NULL};
 		if (envp) {
 			execve("/bin/sh", (char **)argv, (char **)envp);
 		} else {
 			execv("/bin/sh", (char **)argv);
 		}
 		_exit(127);
 	} else {
 		if (waitpid(pid, &status, 0) < 0)
 			goto done;
 		doneflags |= F_WAITPID;
 	}
 
 done:
 	if (doneflags & F_SIGINT)
 		sigaction(SIGINT, &oldsaint, NULL);
 	if (doneflags & F_SIGQUIT)
 		sigaction(SIGQUIT, &oldsaquit, NULL);
 	if (doneflags & F_SIGMASK)
 		sigprocmask(SIG_SETMASK, &oldmask, NULL);
 
 	/* no way to report other errors, use 127 (= shell termination) */
 	if (!(doneflags & F_WAITPID))
 		return 127;
 	if (WIFEXITED(status))
 		return WEXITSTATUS(status);
 	if (WIFSIGNALED(status))
 		return -WTERMSIG(status);
 	return 127;
 }

contrib/chg/util.h

@@ -1,31 +1,32 b''
 /*
  * Utility functions
  *
  * Copyright (c) 2011 Yuya Nishihara <[e-mail]>
  *
  * This software may be used and distributed according to the terms of the
  * GNU General Public License version 2 or any later version.
  */
 
 #ifndef UTIL_H_
 #define UTIL_H_
 
 #ifdef __GNUC__
 #define PRINTF_FORMAT_ __attribute__((format(printf, 1, 2)))
 #else
 #define PRINTF_FORMAT_
 #endif
 
 void abortmsg(const char *fmt, ...) PRINTF_FORMAT_;
 void abortmsgerrno(const char *fmt, ...) PRINTF_FORMAT_;
 
 void enablecolor(void);
 void enabledebugmsg(void);
 void debugmsg(const char *fmt, ...) PRINTF_FORMAT_;
 
+void fchdirx(int dirfd);
 void *mallocx(size_t size);
 void *reallocx(void *ptr, size_t size);
 
 int runshellcmd(const char *cmd, const char *envp[], const char *cwd);
 
 #endif  /* UTIL_H_ */