fix declaration issue

Makefile

@@ -0,0 +1,26 @@
+# Makefile for strict C89/C90 compatibility
+# Compiles all samples in src/c90/ with -std=c90 -pedantic -Wall -Wextra -Werror
+
+.PHONY: all clean
+
+CC := gcc
+CFLAGS := -std=c90 -pedantic -Wall -Wextra -Werror
+SRCDIR := src/c90
+BINDIR := bin
+SOURCES := $(wildcard $(SRCDIR)/*.c)
+BINS := $(SOURCES:$(SRCDIR)/%.c=$(BINDIR)/%)
+
+all: $(BINS)
+
+$(BINDIR)/%: $(SRCDIR)/%.c | $(BINDIR)
+	$(CC) $(CFLAGS) -o $@ $<
+
+$(BINDIR):
+	mkdir -p $(BINDIR)
+
+clean:
+	rm -rf $(BINDIR)
+
+print:
+	@echo "Strict C90 binaries in bin/:"
+	@ls $(BINDIR)

src/c90/metric_server.c

@@ -55,11 +55,10 @@ static void handle_client(int client_sock) {
     unsigned char payload[BUF_SIZE];
 
     while (1) {
+        unsigned char type = 0;
+        unsigned short len = 0;
         if (recv_exact(client_sock, header, HEADER_SIZE) != HEADER_SIZE) break;
 
-        unsigned char type = header[0];
-        unsigned short len = (header[1] << 8) | header[2];
-
         if (len > 0) {
             if (recv_exact(client_sock, payload, len) != len) break;
         }
@@ -67,8 +66,9 @@ static void handle_client(int client_sock) {
         if (type == MSG_PING) {
             send_message(client_sock, MSG_PONG, NULL, 0);
         } else if (type == MSG_METRIC_REQ) {
+            double val;
             payload[len] = '\0'; /* null-terminate */
-            double val = get_metric((char*)payload);
+            val = get_metric((char*)payload);
             if (val < 0) {
                 const char *err = "Unknown metric";
                 send_message(client_sock, MSG_ERROR, err, strlen(err));