xz: Don't modify argv[].

The code that parses --memlimit options and --block-list modified
the argv[] when parsing the option string from optarg. This was
visible in "ps auxf" and such and could be confusing. I didn't
understand it back in the day when I wrote that code. Now a copy
is allocated when modifiable strings are needed.

diff --git a/src/xz/args.c b/src/xz/args.c
index 8953aa59cefc3504ed76f4375946847d44478da2..3d09bd64f4d655e0aa0a5cec6032acd959a3ee6b 100644 (file)
--- a/src/xz/args.c
+++ b/src/xz/args.c
@@ -32,7 +32,7 @@ const char stdin_filename[] = "(stdin)";
 /// Parse and set the memory usage limit for compression, decompression,
 /// and/or multithreaded decompression.
 static void
-parse_memlimit(const char *name, const char *name_percentage, char *str,
+parse_memlimit(const char *name, const char *name_percentage, const char *str,
                bool set_compress, bool set_decompress, bool set_mtdec)
 {
        bool is_percentage = false;
@@ -40,9 +40,18 @@ parse_memlimit(const char *name, const char *name_percentage, char *str,
 
        const size_t len = strlen(str);
        if (len > 0 && str[len - 1] == '%') {
-               str[len - 1] = '\0';
+               // Make a copy so that we can get rid of %.
+               //
+               // In the past str wasn't const and we modified it directly
+               // but that modified argv[] and thus affected what was visible
+               // in "ps auxf" or similar tools which was confusing. For
+               // example, --memlimit=50% would show up as --memlimit=50
+               // since the percent sign was overwritten here.
+               char *s = xstrdup(str);
+               s[len - 1] = '\0';
                is_percentage = true;
-               value = str_to_uint64(name_percentage, str, 1, 100);
+               value = str_to_uint64(name_percentage, s, 1, 100);
+               free(s);
        } else {
                // On 32-bit systems, SIZE_MAX would make more sense than
                // UINT64_MAX. But use UINT64_MAX still so that scripts
@@ -57,8 +66,12 @@ parse_memlimit(const char *name, const char *name_percentage, char *str,
 
 
 static void
-parse_block_list(char *str)
+parse_block_list(const char *str_const)
 {
+       // We need a modifiable string in the for-loop.
+       char *str_start = xstrdup(str_const);
+       char *str = str_start;
+
        // It must be non-empty and not begin with a comma.
        if (str[0] == '\0' || str[0] == ',')
                message_fatal(_("%s: Invalid argument to --block-list"), str);
@@ -113,6 +126,8 @@ parse_block_list(char *str)
 
        // Terminate the array.
        opt_block_list[count] = 0;
+
+       free(str_start);
        return;
 }