Disable the memory usage limiter by default.

For several people, the limiter causes bigger problems that
it solves, so it is better to have it disabled by default.
Those who want to have a limiter by default need to enable
it via the environment variable XZ_DEFAULTS.

Support for environment variable XZ_DEFAULTS was added. It is
parsed before XZ_OPT and technically identical with it. The
intended uses differ quite a bit though; see the man page.

The memory usage limit can now be set separately for
compression and decompression using --memlimit-compress and
--memlimit-decompress. To set both at once, -M or --memlimit
can be used. --memory was retained as a legacy alias for
--memlimit for backwards compatibility.

The semantics of --info-memory were changed in backwards
incompatible way. Compatibility wasn't meaningful due to
changes in the memory usage limiter functionality.

The memory usage limiter info is no longer shown at the
bottom of xz --long -help.

The memory usage limiter support for removed completely from xzdec.

xz's man page was updated to match the above changes. Various
unrelated fixes were also made to the man page.

1 files changed, 58 insertions, 29 deletions

diff --git a/src/xz/args.c b/src/xz/args.c
index 7468a496..d28a3d40 100644
--- a/src/xz/args.c
+++ b/src/xz/args.c
@@ -28,6 +28,32 @@ bool opt_robot = false;
 const char *const stdin_filename = "(stdin)";
 
 
+/// Parse and set the memory usage limit for compression and/or decompression.
+static void
+parse_memlimit(const char *name, const char *name_percentage, char *str,
+		bool set_compress, bool set_decompress)
+{
+	bool is_percentage = false;
+	uint64_t value;
+
+	const size_t len = strlen(str);
+	if (len > 0 && str[len - 1] == '%') {
+		str[len - 1] = '\0';
+		is_percentage = true;
+		value = str_to_uint64(name_percentage, str, 1, 100);
+	} else {
+		// On 32-bit systems, SIZE_MAX would make more sense than
+		// UINT64_MAX. But use UINT64_MAX still so that scripts
+		// that assume > 4 GiB values don't break.
+		value = str_to_uint64(name, str, 0, UINT64_MAX);
+	}
+
+	hardware_memlimit_set(
+			value, set_compress, set_decompress, is_percentage);
+	return;
+}
+
+
 static void
 parse_real(args_info *args, int argc, char **argv)
 {
@@ -45,6 +71,8 @@ parse_real(args_info *args, int argc, char **argv)
 		OPT_NO_SPARSE,
 		OPT_FILES,
 		OPT_FILES0,
+		OPT_MEM_COMPRESS,
+		OPT_MEM_DECOMPRESS,
 		OPT_NO_ADJUST,
 		OPT_INFO_MEMORY,
 		OPT_ROBOT,
@@ -75,8 +103,11 @@ parse_real(args_info *args, int argc, char **argv)
 		// Basic compression settings
 		{ "format",       required_argument, NULL,  'F' },
 		{ "check",        required_argument, NULL,  'C' },
+		{ "memlimit-compress",   required_argument, NULL, OPT_MEM_COMPRESS },
+		{ "memlimit-decompress", required_argument, NULL, OPT_MEM_DECOMPRESS },
+		{ "memlimit",     required_argument, NULL,  'M' },
+		{ "memory",       required_argument, NULL,  'M' }, // Old alias
 		{ "no-adjust",    no_argument,       NULL,  OPT_NO_ADJUST },
-		{ "memory",       required_argument, NULL,  'M' },
 		{ "threads",      required_argument, NULL,  'T' },
 
 		{ "extreme",      no_argument,       NULL,  'e' },
@@ -104,7 +135,7 @@ parse_real(args_info *args, int argc, char **argv)
 		{ "long-help",    no_argument,       NULL,  'H' },
 		{ "version",      no_argument,       NULL,  'V' },
 
-		{ NULL,                 0,                 NULL,   0 }
+		{ NULL,           0,                 NULL,   0 }
 	};
 
 	int c;
@@ -118,28 +149,25 @@ parse_real(args_info *args, int argc, char **argv)
 			coder_set_preset(c - '0');
 			break;
 
-		// --memory
-		case 'M': {
-			// Support specifying the limit as a percentage of
-			// installed physical RAM.
-			size_t len = strlen(optarg);
-			if (len > 0 && optarg[len - 1] == '%') {
-				optarg[len - 1] = '\0';
-				hardware_memlimit_set_percentage(
-						str_to_uint64(
-						"memory%", optarg, 1, 100));
-			} else {
-				// On 32-bit systems, SIZE_MAX would make more
-				// sense than UINT64_MAX. But use UINT64_MAX
-				// still so that scripts that assume > 4 GiB
-				// values don't break.
-				hardware_memlimit_set(str_to_uint64(
-						"memory", optarg,
-						0, UINT64_MAX));
-			}
+		// --memlimit-compress
+		case OPT_MEM_COMPRESS:
+			parse_memlimit("memlimit-compress",
+					"memlimit-compress%", optarg,
+					true, false);
+			break;
 
+		// --memlimit-decompress
+		case OPT_MEM_DECOMPRESS:
+			parse_memlimit("memlimit-decompress",
+					"memlimit-decompress%", optarg,
+					false, true);
+			break;
+
+		// --memlimit
+		case 'M':
+			parse_memlimit("memlimit", "memlimit%", optarg,
+					true, true);
 			break;
-		}
 
 		// --suffix
 		case 'S':
@@ -179,7 +207,7 @@ parse_real(args_info *args, int argc, char **argv)
 		// --info-memory
 		case OPT_INFO_MEMORY:
 			// This doesn't return.
-			message_memlimit();
+			hardware_memlimit_show();
 
 		// --help
 		case 'h':
@@ -384,9 +412,9 @@ parse_real(args_info *args, int argc, char **argv)
 
 
 static void
-parse_environment(args_info *args, char *argv0)
+parse_environment(args_info *args, char *argv0, const char *varname)
 {
-	char *env = getenv("XZ_OPT");
+	char *env = getenv(varname);
 	if (env == NULL)
 		return;
 
@@ -415,8 +443,8 @@ parse_environment(args_info *args, char *argv0)
 			if (++argc == my_min(
 					INT_MAX, SIZE_MAX / sizeof(char *)))
 				message_fatal(_("The environment variable "
-						"XZ_OPT contains too many "
-						"arguments"));
+						"%s contains too many "
+						"arguments"), varname);
 		}
 	}
 
@@ -504,8 +532,9 @@ args_parse(args_info *args, int argc, char **argv)
 		}
 	}
 
-	// First the flags from environment
-	parse_environment(args, argv[0]);
+	// First the flags from the environment
+	parse_environment(args, argv[0], "XZ_DEFAULTS");
+	parse_environment(args, argv[0], "XZ_OPT");
 
 	// Then from the command line
 	parse_real(args, argc, argv);