Replace the fixed-size "cwd" buffer with a dynamically allocated one.

configure.ac

@@ -29,6 +29,7 @@ AC_CHECK_FUNCS([getopt_long])
 AC_CHECK_FUNCS([vsnprintf vasprintf strlcat strtoul memrchr])
 AC_CHECK_FUNCS([fdatasync])
 AC_CHECK_FUNCS([fpathconf sysconf posix_memalign posix_fadvise])
+AC_CHECK_FUNCS([getcwd])
 AC_CHECK_FUNCS([nanosleep])
 AC_CHECK_FUNCS([setitimer])
 AC_CHECK_FUNCS([setproctitle])
@@ -58,7 +59,7 @@ dnl Libraries that may contain key functions.
 AC_SEARCH_LIBS([clock_gettime],[rt])
 
 dnl Items we can't do without.
-AC_CHECK_FUNCS([alarm basename clock_gettime dup2 getcwd memcpy memmove memset mkdir select setlocale strchr strerror strrchr strstr], [], [AC_MSG_ERROR([required function is missing])])
+AC_CHECK_FUNCS([alarm basename clock_gettime dup2 memcpy memmove memset mkdir select setlocale strchr strerror strrchr strstr], [], [AC_MSG_ERROR([required function is missing])])
 AC_CHECK_HEADERS([fcntl.h sys/file.h sys/time.h unistd.h], [], [AC_MSG_ERROR([required header file is missing])])
 
 dnl Make sure all the types we use are defined.

src/include/pv-internal.h

@@ -44,7 +44,6 @@ extern "C" {
 /* Sizes for various statically sized buffers. */
 
 #define PV_SIZEOF_DEFAULT_FORMAT	512
-#define PV_SIZEOF_CWD			4096
 #define PV_SIZEOF_LASTWRITTEN_BUFFER	256
 #define PV_SIZEOF_PREVLINE_BUFFER	1024
 #define PV_FORMAT_ARRAY_MAX		100
@@ -157,7 +156,7 @@ struct pvstate_s {
 	 * Program status *
 	 ******************/
 	struct pvprogramstatus_s {
-		char cwd[PV_SIZEOF_CWD];	 /* current working directory for relative path */
+		nullable_only_string_t cwd;	 /* for relative paths in --watchfd */
 		int current_input_file;		 /* index of current file being read */
 		int exit_status; 		 /* exit status to give (0=OK) */
 		bool terminal_supports_utf8;	 /* whether the terminal supports UTF-8 */

src/pv/state.c

@@ -190,6 +190,7 @@ void pv_state_reset(pvstate_t state)
 pvstate_t pv_state_alloc(void)
 {
 	pvstate_t state;
+	size_t try_size;
 
 	state = calloc(1, sizeof(*state));
 	if (NULL == state)
@@ -209,19 +210,35 @@ pvstate_t pv_state_alloc(void)
 
 	pv_state_reset(state);
 
+#ifdef HAVE_GETCWD
 	/*
 	 * Get the current working directory, if possible, as a base for
 	 * showing relative filenames with --watchfd.
+	 *
+	 * If this fails then --watchfd will fall back to always showing the
+	 * full path.
 	 */
-	if (NULL == getcwd(state->status.cwd, PV_SIZEOF_CWD - 1)) {
-		/* failed - will always show full path. */
-		state->status.cwd[0] = '\0';
+	for (try_size = 32; try_size <= 16384; try_size = try_size * 2) {
+		bool buffer_too_small;
+
+		/*@-mustfreeonly@ *//* splint mis-detects a memory leak here */
+		state->status.cwd = malloc(try_size);
+		/*@+mustfreeonly@ */
+		if (NULL == state->status.cwd)
+			break;
+
+		buffer_too_small = false;
+		if (NULL == getcwd(state->status.cwd, try_size)) {
+			if (errno != ERANGE)
+				buffer_too_small = true;
+			free(state->status.cwd);
+			state->status.cwd = NULL;
+		}
+
+		if (!buffer_too_small)
+			break;
 	}
-	if ('\0' == state->status.cwd[1]) {
-		/* CWD is root directory - always show full path. */
-		state->status.cwd[0] = '\0';
-	}
-	state->status.cwd[PV_SIZEOF_CWD - 1] = '\0';
+#endif	/* HAVE_GETCWD */
 
 	return state;
 }
@@ -360,6 +377,11 @@ void pv_state_free(pvstate_t state)
 		state->control.output_name = NULL;
 	}
 
+	if (NULL != state->status.cwd) {
+		free(state->status.cwd);
+		state->status.cwd = NULL;
+	}
+
 	pv_freecontents_display(&(state->display));
 	pv_freecontents_display(&(state->extra_display));
 

src/pv/watchpid.c

@@ -683,9 +683,12 @@ void pv_watchpid_setname(pvstate_t state, pvwatchfd_t info)
 	memset(info->display_name, 0, PV_SIZEOF_DISPLAY_NAME);
 
 	path_length = strlen(info->file_fdpath);	/* flawfinder: ignore */
-	cwd_length = strlen(state->status.cwd);	/* flawfinder: ignore */
+	cwd_length = 0;
+	if (NULL != state->status.cwd) {
+		cwd_length = strlen(state->status.cwd);	/* flawfinder: ignore */
+	}
 	/* flawfinder: both strings are always \0 terminated. */
-	if (cwd_length > 0 && path_length > cwd_length) {
+	if (cwd_length > 0 && path_length > cwd_length && NULL != state->status.cwd) {
 		if (0 == strncmp(info->file_fdpath, state->status.cwd, cwd_length)) {
 			file_fdpath += cwd_length + 1;
 			path_length -= cwd_length + 1;