fix(makefile)!: improve flags and type casts for stricter build and correctness

- Update Makefile:
  - Change test binary name to `libicmp.test`.
  - Add `-Wpedantic` and `-Wconversion` to global CFLAGS for stricter
    warnings.
  - Add dedicated `TEST_CFLAGS`.
  - Ensure test build uses `TEST_CFLAGS`.
- Refactor code for better correctness.

BREAKING CHANGE: Test binary is now named `libicmp.test` instead of
`test.out` and stricter compiler flags may trigger new warnings or
errors in code outside this patch.

.gitignore

@@ -2,7 +2,7 @@
 *.a
 *.so
 *.so.*
-test.out
+libicmp.test
 .build/
 
 # Object files and dependencies

Makefile

@@ -3,7 +3,7 @@ LIB_STATIC = lib$(LIB_NAME).a
 LIB_SHARED = lib$(LIB_NAME).so
 LIB_VERSION = 1.0.0
 LIB_SHARED_VERSIONED = $(LIB_SHARED).$(LIB_VERSION)
-TEST_BIN = test.out
+TEST_BIN = libicmp.test
 
 # Build configuration
 BUILD_STATIC ?= yes
@@ -21,10 +21,11 @@ include sources.mk
 
 CC = clang
 CPPFLAGS = -std=c99 -I includes -D_POSIX_C_SOURCE=199309L
-CFLAGS = -Wall -Wextra -Werror -pipe
+CFLAGS = -Wall -Wextra -Werror -pipe -Wpedantic -Wconversion
 CFLAGS_SHARED = $(CFLAGS) -fPIC
 LDFLAGS =
 TEST_LDFLAGS = -lcriterion
+TEST_CFLAGS = -Wall -Wextra -Werror -pipe
 
 OBJ_DIR = .build
 OBJ_DIR_STATIC = $(OBJ_DIR)/static
@@ -67,7 +68,7 @@ test: $(TEST_BIN)
 
 $(TEST_BIN): $(TESTS) $(OBJS_STATIC)
 	@mkdir -p $(dir $@)
-	$(CC) $(CPPFLAGS) -I tests $(CFLAGS) $(TEST_LDFLAGS) $^ -o $@
+	$(CC) $(CPPFLAGS) -I tests $(TEST_CFLAGS) $(TEST_LDFLAGS) $^ -o $@
 
 .PHONY: install
 install:

src/packet/parse_ip.c

@@ -44,14 +44,17 @@ icmp_parse_ip_header(const void *buffer, size_t buffer_len, uint8_t *ttl,
 static int
 validate_ip_header(const struct ip_header *hdr, size_t buffer_len)
 {
+	uint8_t ihl;
+	size_t header_len;
+
 	if (4 != (hdr->version_ihl >> 4))
 		return -1;
 
-	uint8_t ihl = hdr->version_ihl & 0x0F;
+	ihl = hdr->version_ihl & 0x0F;
 	if (ihl < 5)
 		return -1;
 
-	size_t header_len = ihl << 2;
+	header_len = (size_t)(ihl << 2);
 	if (header_len > buffer_len)
 		return -1;
 
@@ -61,5 +64,5 @@ validate_ip_header(const struct ip_header *hdr, size_t buffer_len)
 static size_t
 extract_ip_header_length(uint8_t version_ihl)
 {
-	return (version_ihl & 0x0F) << 2;
+	return (size_t)((version_ihl & 0x0F) << 2);
 }

src/recv/core/process_single_packet.c

@@ -1,5 +1,6 @@
 #include "internal/icmp_recv.h"
 
+// TODO: check ssize_t -> size_t cast
 void
 recv_process_single_packet(uint8_t *buffer, ssize_t len, icmp_callback_t cb,
 							void *userdata)
@@ -10,11 +11,11 @@ recv_process_single_packet(uint8_t *buffer, ssize_t len, icmp_callback_t cb,
 	const void *payload;
 	size_t payload_len, ip_hdr_len;
 
-	if (recv_parse_packet(buffer, len, &type, &code, &ttl, &src_addr,
+	if (recv_parse_packet(buffer, (size_t)(len), &type, &code, &ttl, &src_addr,
 						&payload, &payload_len, &ip_hdr_len) < 0)
 		return;
 	recv_build_reply(&reply, type, code, ttl, src_addr, payload, payload_len,
 					buffer, ip_hdr_len);
-	reply.ip_payload_len = len - ip_hdr_len;
+	reply.ip_payload_len = (size_t)(len) - ip_hdr_len;
 	cb(&reply, userdata);
 }

src/send/api/raw.c

@@ -36,7 +36,7 @@ icmp_send_raw(icmp_handle_t *h, uint8_t type, uint8_t code,
 		return -1;
 	}
 
-	return send_to_destination(h, buffer, packet_len, dest, ttl);
+	return send_to_destination(h, buffer, (size_t)(packet_len), dest, ttl);
 }
 
 static int

src/utils/checksum.c

@@ -16,7 +16,7 @@ icmp_checksum(const void *data, size_t len)
 	sum = sum_words(data, len);
 	sum = fold_carries(sum);
 
-	return ~sum;
+	return (uint16_t)~sum;
 }
 
 /* Sum all 16-bit words */
@@ -42,7 +42,7 @@ sum_words(const uint8_t *data, size_t len)
 
 	/* Handle odd byte if present */
 	if (len & 1)
-		sum += *ptr << 8;
+		sum += (uint32_t)(*ptr << 8);
 
 	return sum;
 }
@@ -53,12 +53,12 @@ fold_carries(uint32_t sum)
 {
 	while (sum >> 16)
 		sum = (sum & 0xFFFF) + (sum >> 16);
-	return sum;
+	return (uint16_t)sum;
 }
 
 /* Read 16-bit word in network byte order (big-endian) */
 static inline uint16_t
 read_be16(const uint8_t *ptr)
 {
-	return (*ptr << 8) | ptr[1];
+	return (uint16_t)((*ptr << 8) | ptr[1]);
 }