From 4d1c070b813f3b3b64bd8bf96723756041840ac0 Mon Sep 17 00:00:00 2001
From: Carlos Maiolino <cem@toxiclabs.cc>
Date: Sat, 6 Sep 2025 12:59:56 +0200
Subject: Create shared library

Play with shared libs. Building the same library with different
functionalities and loading them at runtime, separately.

Fun way to see how we can change runtime behavior without recompiling
everything.

Signed-off-by: Carlos Maiolino <cem@toxiclabs.cc>
---
 C/HF/chap8/Makefile              |  24 ++++++++++++++++++++++++
 C/HF/chap8/bin/ecat              | Bin 12944 -> 0 bytes
 C/HF/chap8/bin/libs/libencrypt.a | Bin 3754 -> 0 bytes
 C/HF/chap8/src/libs/encrypt2.c   |  11 +++++++++++
 4 files changed, 35 insertions(+)
 delete mode 100755 C/HF/chap8/bin/ecat
 delete mode 100644 C/HF/chap8/bin/libs/libencrypt.a
 create mode 100644 C/HF/chap8/src/libs/encrypt2.c

(limited to 'C')

diff --git a/C/HF/chap8/Makefile b/C/HF/chap8/Makefile
index df3283e..8377c1b 100644
--- a/C/HF/chap8/Makefile
+++ b/C/HF/chap8/Makefile
@@ -13,3 +13,27 @@ bin/libs/xor.o: $(INCLUDE_DIR)/libs/xor.h src/libs/xor.c
 
 bin/libs/encrypt.o: $(INCLUDE_DIR)/libs/encrypt.h src/libs/encrypt.c
 	cc -I $(INCLUDE_DIR) -c src/libs/encrypt.c -o bin/libs/encrypt.o
+
+# Create DSO and PIC versions
+#
+ecatS: bin/libs/libencrypt.a
+	cc -I $(INCLUDE_DIR) -L bin/libs -o bin/ecats src/ecat.c -lencrypts
+
+bin/libs/libencrypts.so: bin/libs/xor-pic.o bin/libs/encrypt-pic.o
+	cc -I $(INCLUDE_DIR) -shared -o bin/libs/libencrypts.so bin/libs/xor-pic.o bin/libs/encrypt-pic.o
+
+# This creates the same lib with a broken encrypt_arr call.
+# We can run the same program passing the different lib at runtime
+# and change the behavior of encrypt_arr at runtime
+bin/broken_libs/libencrypts.so: bin/libs/xor-pic.o bin/libs/encrypt2-pic.o
+	cc -I $(INCLUDE_DIR) -shared -o bin/broken_libs/libencrypts.so bin/libs/xor-pic.o bin/libs/encrypt2-pic.o
+
+
+bin/libs/xor-pic.o: $(INCLUDE_DIR)/libs/xor.h src/libs/xor.c
+	cc -fPIC -I $(INCLUDE_DIR) -c src/libs/xor.c -o bin/libs/xor-pic.o
+
+bin/libs/encrypt-pic.o: $(INCLUDE_DIR)/libs/encrypt.h src/libs/encrypt.c
+	cc -fPIC -I $(INCLUDE_DIR) -c src/libs/encrypt.c -o bin/libs/encrypt-pic.o
+
+bin/libs/encrypt2-pic.o: $(INCLUDE_DIR)/libs/encrypt.h src/libs/encrypt2.c
+	cc -fPIC -I $(INCLUDE_DIR) -c src/libs/encrypt2.c -o bin/libs/encrypt2-pic.o
diff --git a/C/HF/chap8/bin/ecat b/C/HF/chap8/bin/ecat
deleted file mode 100755
index 1167d31..0000000
Binary files a/C/HF/chap8/bin/ecat and /dev/null differ
diff --git a/C/HF/chap8/bin/libs/libencrypt.a b/C/HF/chap8/bin/libs/libencrypt.a
deleted file mode 100644
index f609c17..0000000
Binary files a/C/HF/chap8/bin/libs/libencrypt.a and /dev/null differ
diff --git a/C/HF/chap8/src/libs/encrypt2.c b/C/HF/chap8/src/libs/encrypt2.c
new file mode 100644
index 0000000..939df8b
--- /dev/null
+++ b/C/HF/chap8/src/libs/encrypt2.c
@@ -0,0 +1,11 @@
+#include <stdio.h>
+#include <libs/encrypt.h>
+
+void encrypt(char *message, encrypt_fn_t encrypt_fn) {
+	encrypt_fn(message);
+}
+
+void encrypt_arr(char *message, encrypt_arr_t fn_arr, int size)
+{
+	printf("BROKEN LIB\n");
+}
-- 
cgit v1.2.3