refactor: standardize error reporting on the log module

- Add log_perror() helper (context + strerror(errno)) to the log module
- Replace all bare perror() calls with log_perror() so errors are routed
  through the unified logger (stderr sink + optional --log-file sink)
- Convert fprintf(stderr, "Error:/Warning: ...") in client code to
  log_message(); raw fprintf kept only for progress/stats output

src/client/client_cli.c

@@ -60,7 +60,7 @@ static bool parse_positive_int(const char* s, int* out_val) {
 static int set_string_option(char** dest, const char* value, const char* option_name) {
   char* dup = str_dup(value);
   if (!dup) {
-    fprintf(stderr, "Error: memory allocation failed for %s\n", option_name);
+    log_message(LOG_LEVEL_ERROR, "memory allocation failed for %s", option_name);
     return -1;
   }
   free(*dest);
@@ -71,7 +71,7 @@ static int set_string_option(char** dest, const char* value, const char* option_
 /* Parse a string as a positive integer into *dest. Returns true on success, false on error. */
 static int set_positive_int_option(int* dest, const char* value, const char* option_name) {
   if (!parse_positive_int(value, dest)) {
-    fprintf(stderr, "Error: %s must be a positive integer\n", option_name);
+    log_message(LOG_LEVEL_ERROR, "%s must be a positive integer", option_name);
     return -1;
   }
   return 0;
@@ -80,7 +80,7 @@ static int set_positive_int_option(int* dest, const char* value, const char* opt
 /* Parse a string as a non-negative integer into *dest. Returns true on success, false on error. */
 static int set_nonneg_int_option(int* dest, const char* value, const char* option_name) {
   if (!parse_nonneg_int(value, dest)) {
-    fprintf(stderr, "Error: %s must be a non-negative integer\n", option_name);
+    log_message(LOG_LEVEL_ERROR, "%s must be a non-negative integer", option_name);
     return -1;
   }
   return 0;
@@ -94,7 +94,7 @@ static int parse_ull_arg(const char* val, unsigned long long* out, const char* o
   errno = 0;
   unsigned long long v = strtoull(val, &end, 10);
   if (errno != 0 || *end != '\0') {
-    fprintf(stderr, "Error: %s must be a non-negative integer\n", optname);
+    log_message(LOG_LEVEL_ERROR, "%s must be a non-negative integer", optname);
     return -1;
   }
   *out = v;
@@ -106,13 +106,13 @@ static int config_add_pattern(char*** patterns, int* count, const char* value,
                               const char* optname) {
   char** tmp = realloc(*patterns, (*count + 1) * sizeof(char*));
   if (!tmp) {
-    fprintf(stderr, "Error: memory allocation failed for %s\n", optname);
+    log_message(LOG_LEVEL_ERROR, "memory allocation failed for %s", optname);
     return -1;
   }
   *patterns = tmp;
   char* dup = str_dup(value);
   if (!dup) {
-    fprintf(stderr, "Error: memory allocation failed for %s\n", optname);
+    log_message(LOG_LEVEL_ERROR, "memory allocation failed for %s", optname);
     return -1;
   }
   (*patterns)[(*count)++] = dup;
@@ -215,7 +215,7 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
     if (entry) {
       if (entry->kind != OPT_FLAG) {
         if (i + 1 >= argc) {
-          fprintf(stderr, "Error: missing argument for %s\n", entry->name);
+          log_message(LOG_LEVEL_ERROR, "missing argument for %s", entry->name);
           return -1;
         }
         if (apply_table_option(config, entry, argv[++i]) != 0)
@@ -241,7 +241,7 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
       if (set_positive_int_option(&config->ssh_port, argv[++i], "-p") != 0)
         return -1;
       if (config->ssh_port > 65535) {
-        log_message(LOG_LEVEL_ERROR, "SSH port must be 1-65535\n");
+        log_message(LOG_LEVEL_ERROR, "SSH port must be 1-65535");
         return -1;
       }
     } else if (opt_is(argv[i], "--exclude", NULL) && i + 1 < argc) {
@@ -259,7 +259,7 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
       if (val >= DELTA_BLOCK_SIZE_MIN && val <= DELTA_BLOCK_SIZE_MAX)
         config->delta_block_size = (uint32_t)val;
       else
-        fprintf(stderr, "Warning: --delta-block value %llu out of range, using default\n", val);
+        log_message(LOG_LEVEL_WARNING, "--delta-block value %llu out of range, using default", val);
     } else if (opt_is(argv[i], "--delta-max", NULL) && i + 1 < argc) {
       unsigned long long val;
       if (parse_ull_arg(argv[++i], &val, "--delta-max") != 0)
@@ -267,7 +267,7 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
       if (val >= DELTA_MIN_FILE_SIZE)
         config->delta_max_file_size = val;
       else
-        fprintf(stderr, "Warning: --delta-max value %llu too small, using default\n", val);
+        log_message(LOG_LEVEL_WARNING, "--delta-max value %llu too small, using default", val);
     } else if (opt_is(argv[i], "-c", "-z")) {
       config->use_compression = true;
       log_message(LOG_LEVEL_INFO, "Enabled Compression");
@@ -276,7 +276,7 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
         long level = strtol(argv[i + 1], &end_ptr, 10);
         if (*end_ptr == '\0') {
           if (level < 1 || level > 22) {
-            fprintf(stderr, "Error: compression level must be 1-22\n");
+            log_message(LOG_LEVEL_ERROR, "compression level must be 1-22");
             return -1;
           }
           config->compression_level = (int)level;
@@ -298,11 +298,11 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
       log_message(LOG_LEVEL_INFO, "Enabled Chunk Serialization");
     } else if (opt_is(argv[i], "--server-port", NULL) && i + 1 < argc) {
       if (!parse_positive_int(argv[++i], &config->server_port)) {
-        fprintf(stderr, "Error: invalid --server-port value: %s\n", argv[i]);
+        log_message(LOG_LEVEL_ERROR, "invalid --server-port value: %s", argv[i]);
         return -1;
       }
       if (config->server_port > 65535) {
-        fprintf(stderr, "Error: server port must be 1-65535\n");
+        log_message(LOG_LEVEL_ERROR, "server port must be 1-65535");
         return -1;
       }
     } else if (opt_is(argv[i], "--bwlimit", NULL) && i + 1 < argc) {
@@ -310,11 +310,11 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
       if (parse_ull_arg(argv[++i], &kbps, "--bwlimit") != 0)
         return -1;
       if (kbps == 0) {
-        fprintf(stderr, "Error: --bwlimit must be a positive integer\n");
+        log_message(LOG_LEVEL_ERROR, "--bwlimit must be a positive integer");
         return -1;
       }
       if (kbps > ULLONG_MAX / 1024) {
-        fprintf(stderr, "Error: --bwlimit value too large\n");
+        log_message(LOG_LEVEL_ERROR, "--bwlimit value too large");
         return -1;
       }
       io_set_bwlimit(kbps * 1024);
@@ -324,7 +324,7 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
       if (parse_ull_arg(argv[++i], &val, "--chunk-size") != 0)
         return -1;
       if (val == 0) {
-        fprintf(stderr, "Error: --chunk-size must be a positive integer\n");
+        log_message(LOG_LEVEL_ERROR, "--chunk-size must be a positive integer");
         return -1;
       }
       config->chunk_size = val;
@@ -336,7 +336,7 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
       }
       FILE* lf = fopen(argv[++i], "a");
       if (!lf) {
-        fprintf(stderr, "Error: could not open log file '%s': %s\n", argv[i], strerror(errno));
+        log_message(LOG_LEVEL_ERROR, "could not open log file '%s': %s", argv[i], strerror(errno));
         return -1;
       }
       config->log_file = lf;
@@ -358,7 +358,7 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
       if (set_positive_int_option(&config->compression_level, argv[++i], "--compress-level") != 0)
         return -1;
       if (config->compression_level < 1 || config->compression_level > 22) {
-        fprintf(stderr, "Error: --compress-level must be between 1 and 22\n");
+        log_message(LOG_LEVEL_ERROR, "--compress-level must be between 1 and 22");
         return -1;
       }
     } else if (argv[i][0] == '-') {
@@ -381,7 +381,7 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
 static int read_patterns_from_file(const char* filepath, char*** patterns, int* count) {
   FILE* fp = fopen(filepath, "r");
   if (!fp) {
-    fprintf(stderr, "Error: could not open pattern file '%s': %s\n", filepath, strerror(errno));
+    log_message(LOG_LEVEL_ERROR, "could not open pattern file '%s': %s", filepath, strerror(errno));
     return -1;
   }
   char* line = NULL;
@@ -420,7 +420,7 @@ int main(int argc, char* argv[]) {
   bool config_owned_by_pipeline = false;
   Config* config = config_create();
   if (!config) {
-    fprintf(stderr, "Error: failed to allocate config\n");
+    log_message(LOG_LEVEL_ERROR, "failed to allocate config");
     return 1;
   }
   config->save_to_disk = save_to_disk;
@@ -441,20 +441,20 @@ int main(int argc, char* argv[]) {
     free(config->receive_root_directory);
     config->send_directory = str_dup(argv[positional_args[0]]);
     if (!config->send_directory) {
-      fprintf(stderr, "Error: memory allocation failed\n");
+      log_message(LOG_LEVEL_ERROR, "memory allocation failed");
       exit_code = 1;
       goto cleanup;
     }
     config->receive_root_directory = str_dup(argv[positional_args[1]]);
     if (!config->receive_root_directory) {
-      fprintf(stderr, "Error: memory allocation failed\n");
+      log_message(LOG_LEVEL_ERROR, "memory allocation failed");
       exit_code = 1;
       goto cleanup;
     }
     config->save_to_disk = true;
     config_parse_ssh_dest(config);
   } else if (positional_count == 1) {
-    fprintf(stderr, "Error: missing destination argument\n");
+    log_message(LOG_LEVEL_ERROR, "missing destination argument");
     print_usage();
     exit_code = 1;
     goto cleanup;
@@ -462,7 +462,7 @@ int main(int argc, char* argv[]) {
     if (!config->send_directory && env_source) {
       config->send_directory = str_dup(env_source);
       if (!config->send_directory) {
-        fprintf(stderr, "Error: memory allocation failed\n");
+        log_message(LOG_LEVEL_ERROR, "memory allocation failed");
         exit_code = 1;
         goto cleanup;
       }
@@ -470,7 +470,7 @@ int main(int argc, char* argv[]) {
     if (!config->receive_root_directory && env_dest) {
       config->receive_root_directory = str_dup(env_dest);
       if (!config->receive_root_directory) {
-        fprintf(stderr, "Error: memory allocation failed\n");
+        log_message(LOG_LEVEL_ERROR, "memory allocation failed");
         exit_code = 1;
         goto cleanup;
       }

src/client/client_send.c

@@ -42,7 +42,7 @@ static ScannerOptions scanner_options_from_config(const Config* config, int num_
 static Client* connect_transfer_client(const Config* config) {
   if (config->transport == TRANSPORT_SSH) {
     if (config->use_sendfile) {
-      fprintf(stderr, "Error: -f/--sendfile is not supported with SSH transport\n");
+      log_message(LOG_LEVEL_ERROR, "-f/--sendfile is not supported with SSH transport");
       return NULL;
     }
     return client_connect_ssh(config->ssh_destination, config->ssh_port,
@@ -377,7 +377,7 @@ static int send_chunks_multithreaded(void* pipeline_context) {
   Client* client = connect_transfer_client(context->config);
   if (!client) {
     if (context->config->transport == TRANSPORT_TCP)
-      fprintf(stderr, "Error: could not connect to server%s\n",
+      log_message(LOG_LEVEL_ERROR, "could not connect to server%s",
               context->config->use_tls ? " via TLS" : "");
     pipeline_cancel(context);
     mark_sender_done(context);
@@ -425,7 +425,7 @@ static int send_chunks_multithreaded(void* pipeline_context) {
       return thrd_error;
     }
     if (send_chunk(client, current_chunk, context->config) != 0) {
-      fprintf(stderr, "Error: unexpected error while sending chunk\n");
+      log_message(LOG_LEVEL_ERROR, "unexpected error while sending chunk");
       chunk_destroy(current_chunk);
       pipeline_cancel(context);
       disconnect_transfer_client(client);
@@ -585,7 +585,7 @@ int send_files(Config* config) {
   Client* client = connect_transfer_client(config);
   if (!client) {
     if (config->transport == TRANSPORT_TCP)
-      fprintf(stderr, "Error: could not connect to server%s\n", config->use_tls ? " via TLS" : "");
+      log_message(LOG_LEVEL_ERROR, "could not connect to server%s", config->use_tls ? " via TLS" : "");
     return 1;
   }
   ProtocolSession session;
@@ -736,7 +736,7 @@ int send_files_multithreaded(Config* config) {
     sender_created = (thrd_create(&sender, send_chunks_multithreaded, context) == thrd_success);
 
   if (!scanner_created || !loader_created || !sender_created) {
-    perror("Error creating threads");
+    log_perror("Error creating threads");
     pipeline_cancel(context);
     mtx_lock(&context->mutex_progress);
     context->sender_done = true;
@@ -756,7 +756,7 @@ int send_files_multithreaded(Config* config) {
   if (config->show_progress) {
     progress_created = (thrd_create(&progress, progress_thread_fn, context) == thrd_success);
     if (!progress_created) {
-      perror("Error creating progress thread");
+      log_perror("Error creating progress thread");
       /* Non-fatal; continue without progress reporting */
     }
   }

src/client/client_validation.c

@@ -1,37 +1,38 @@
 #include "client_validation.h"
+#include "log.h"
 #include "usage.h"
 #include <stdio.h>
 
 /* Validate config after parsing. Returns true if valid. */
 bool validate_config(const Config* config) {
   if (!config->send_directory || !config->receive_root_directory) {
-    fprintf(stderr, "Error: source and destination directories are required\n");
+    log_message(LOG_LEVEL_ERROR, "source and destination directories are required");
     print_usage();
     return false;
   }
   if (config->use_sendfile && (config->use_chunk_serialization || config->use_compression)) {
-    fprintf(stderr, "Error: -f/--sendfile cannot be combined with -c (compression) or -s (chunk "
-                    "serialization)\n");
+    log_message(LOG_LEVEL_ERROR, "-f/--sendfile cannot be combined with -c (compression) or -s "
+                                 "(chunk serialization)");
     return false;
   }
   if (config->transport == TRANSPORT_SSH && config->use_sendfile) {
-    fprintf(stderr, "Error: -f/--sendfile is not supported with SSH transport\n");
+    log_message(LOG_LEVEL_ERROR, "-f/--sendfile is not supported with SSH transport");
     return false;
   }
   if (config->use_incremental && config->use_chunk_serialization) {
-    fprintf(stderr, "Error: --incremental is not supported with -s (chunk serialization)\n");
+    log_message(LOG_LEVEL_ERROR, "--incremental is not supported with -s (chunk serialization)");
     return false;
   }
   if (config->use_delta && !config->use_incremental) {
-    fprintf(stderr, "Error: --delta requires --incremental\n");
+    log_message(LOG_LEVEL_ERROR, "--delta requires --incremental");
     return false;
   }
   if (config->use_delta && config->use_chunk_serialization) {
-    fprintf(stderr, "Error: --delta cannot be combined with -s (chunk serialization)\n");
+    log_message(LOG_LEVEL_ERROR, "--delta cannot be combined with -s (chunk serialization)");
     return false;
   }
   if (config->use_delta && config->use_sendfile) {
-    fprintf(stderr, "Error: --delta cannot be combined with -f (sendfile)\n");
+    log_message(LOG_LEVEL_ERROR, "--delta cannot be combined with -f (sendfile)");
     return false;
   }
   if (config->append || config->append_verify) {
@@ -42,7 +43,7 @@ bool validate_config(const Config* config) {
   }
   if (config->use_tls) {
     if (!config->tls_cert || !config->tls_key) {
-      fprintf(stderr, "Error: --tls requires --cert and --key\n");
+      log_message(LOG_LEVEL_ERROR, "--tls requires --cert and --key");
       return false;
     }
   }

src/client/scanner.c

@@ -1,3 +1,4 @@
+#include "log.h"
 #include "scanner.h"
 #include "array_list.h"
 #include "chunk.h"
@@ -226,7 +227,7 @@ static int open_next_directory(DirectoryScanner* scanner) {
   free(de);
   scanner->current_dir = opendir(scanner->current_path);
   if (scanner->current_dir == NULL) {
-    perror("Could not open directory");
+    log_perror("Could not open directory");
     free(scanner->current_path);
     scanner->current_path = NULL;
     scanner->failed = true;
@@ -564,7 +565,7 @@ static bool scan_root_directory(ParallelScanner* ps, const char* root_directory,
                                 ArrayList* subdirs) {
   DIR* dir = opendir(root_directory);
   if (!dir) {
-    perror("Could not open root directory for parallel scan");
+    log_perror("Could not open root directory for parallel scan");
     return false;
   }
   const struct dirent* entry;