Allow giving --debug to enable debugging (but drops setgid).

diff --git a/plocate.cpp b/plocate.cpp
index 371fb533e2fba8d3fe98455dcc15cb28077529fe..c4011c9888b3b0f86c12132b0207dcd951332aa1 100644 (file)
--- a/plocate.cpp
+++ b/plocate.cpp
@@ -32,8 +32,12 @@
 using namespace std;
 using namespace std::chrono;
 
-#define dprintf(...)
-//#define dprintf(...) fprintf(stderr, __VA_ARGS__);
+#define dprintf(...) \
+       do { \
+               if (use_debug) { \
+                       fprintf(stderr, __VA_ARGS__); \
+               } \
+       } while (false)
 
 #include "turbopfor.h"
 
@@ -41,6 +45,7 @@ const char *dbpath = "/var/lib/mlocate/plocate.db";
 bool ignore_case = false;
 bool only_count = false;
 bool print_nul = false;
+bool use_debug = false;
 int64_t limit_matches = numeric_limits<int64_t>::max();
 
 class Serializer {
@@ -590,13 +595,14 @@ int main(int argc, char **argv)
                { "ignore-case", no_argument, 0, 'i' },
                { "limit", required_argument, 0, 'l' },
                { "null", no_argument, 0, '0' },
+               { "debug", no_argument, 0, 'D' },  // Not documented.
                { 0, 0, 0, 0 }
        };
 
        setlocale(LC_ALL, "");
        for (;;) {
                int option_index = 0;
-               int c = getopt_long(argc, argv, "cd:hil:n:0", long_options, &option_index);
+               int c = getopt_long(argc, argv, "cd:hil:n:0D", long_options, &option_index);
                if (c == -1) {
                        break;
                }
@@ -620,11 +626,24 @@ int main(int argc, char **argv)
                case '0':
                        print_nul = true;
                        break;
+               case 'D':
+                       use_debug = true;
+                       break;
                default:
                        exit(1);
                }
        }
 
+       if (use_debug) {
+               // Debug information would leak information about which files exist,
+               // so drop setgid before we open the file; one would either need to run
+               // as root, or use a locally-built file.
+               if (setgid(getgid()) != 0) {
+                       perror("setgid");
+                       exit(EXIT_FAILURE);
+               }
+       }
+
        vector<Needle> needles;
        for (int i = optind; i < argc; ++i) {
                Needle needle;