From 239a646210b25b11c4e5e6a2113d932c45a33ffe Mon Sep 17 00:00:00 2001
From: Jan200101 <sentrycraft123@gmail.com>
Date: Tue, 27 Dec 2022 15:18:45 +0100
Subject: initial commit

---
 .gitignore     |  1 +
 CMakeLists.txt | 35 +++++++++++++++++++++++++++++++++++
 defines.h      | 11 +++++++++++
 print.c        |  9 +++++++++
 print.h        |  6 ++++++
 shim.c         | 27 +++++++++++++++++++++++++++
 wrap.c         | 19 +++++++++++++++++++
 wrap.h         | 21 +++++++++++++++++++++
 8 files changed, 129 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 CMakeLists.txt
 create mode 100644 defines.h
 create mode 100644 print.c
 create mode 100644 print.h
 create mode 100644 shim.c
 create mode 100644 wrap.c
 create mode 100644 wrap.h

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..378eac2
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+build
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..a7dd4ed
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,35 @@
+cmake_minimum_required(VERSION 3.10)
+
+set(CFLAGS
+    -Wall -Wextra -Wfloat-equal
+    -Wstrict-overflow=5 -Wunreachable-code
+    -Wundef -Wcast-qual -Wconversion 
+    -Wswitch-default -Wmissing-include-dirs
+    -Wshadow -Wstrict-aliasing -Winit-self
+    -Wcast-align -Wpointer-arith
+    -Wno-unused-parameter -Wuninitialized
+    -D_GNU_SOURCE
+)
+
+list(APPEND
+    SOURCES
+    ${CMAKE_CURRENT_SOURCE_DIR}/print.c
+    ${CMAKE_CURRENT_SOURCE_DIR}/print.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/shim.c
+    ${CMAKE_CURRENT_SOURCE_DIR}/wrap.c
+    ${CMAKE_CURRENT_SOURCE_DIR}/wrap.h
+)
+
+project(shim)
+add_library(shim_objects OBJECT ${SOURCES})
+set_property(TARGET shim_objects PROPERTY POSITION_INDEPENDENT_CODE ON)
+set_property(TARGET shim_objects PROPERTY C_VISIBILITY_PRESET hidden)
+set_property(TARGET shim_objects PROPERTY VISIBILITY_INLINES_HIDDEN ON)
+target_compile_options(shim_objects PUBLIC ${CFLAGS})
+
+add_library(shim SHARED $<TARGET_OBJECTS:shim_objects>)
+target_link_libraries(shim LINK_PUBLIC ${CMAKE_DL_LIBS})
+
+add_library(shim_static STATIC $<TARGET_OBJECTS:shim_objects>)
+
+
diff --git a/defines.h b/defines.h
new file mode 100644
index 0000000..6c04a4e
--- /dev/null
+++ b/defines.h
@@ -0,0 +1,11 @@
+#ifndef DEFINES_H
+#define DEFINES_H
+
+#ifndef NDEBUG
+#define DEBUG
+#endif
+
+#define STR(x) #x
+#define XSTR(x) STR(x)
+
+#endif /* DEFINES_H */
diff --git a/print.c b/print.c
new file mode 100644
index 0000000..5b1be08
--- /dev/null
+++ b/print.c
@@ -0,0 +1,9 @@
+#include <string.h>
+#include <unistd.h>
+
+#include "print.h"
+
+void print(const char* str, ...)
+{
+    write(STDOUT_FILENO, str, strlen(str));
+}
diff --git a/print.h b/print.h
new file mode 100644
index 0000000..08099c5
--- /dev/null
+++ b/print.h
@@ -0,0 +1,6 @@
+#ifndef PRINT_H
+#define PRINT_H
+
+void print(const char* str, ...);
+
+#endif
\ No newline at end of file
diff --git a/shim.c b/shim.c
new file mode 100644
index 0000000..b89c748
--- /dev/null
+++ b/shim.c
@@ -0,0 +1,27 @@
+#include <stdlib.h>
+
+#include "print.h"
+#include "wrap.h"
+
+#pragma GCC visibility push(default)
+
+void* malloc(size_t size) {
+    return REAL(malloc)(size);
+}
+
+void free(void* ptr)
+{
+    return REAL(free)(ptr);
+}
+
+void* calloc(size_t nmemb, size_t size)
+{
+    return REAL(calloc)(nmemb, size);
+}
+
+void* realloc(void *ptr, size_t size)
+{
+    return REAL(realloc)(ptr, size);
+}
+
+#pragma GCC visibility pop
diff --git a/wrap.c b/wrap.c
new file mode 100644
index 0000000..5ed0bc8
--- /dev/null
+++ b/wrap.c
@@ -0,0 +1,19 @@
+#include <stddef.h>
+
+#include "wrap.h"
+
+void *(*_REAL(malloc))(size_t size) = NULL;
+void (*_REAL(free))(void *ptr) = NULL;
+void *(*_REAL(calloc))(size_t nmemb, size_t size) = NULL;
+void *(*_REAL(realloc))(void *ptr, size_t size) = NULL;
+
+#ifdef __GNUC__
+void __attribute__((constructor)) __wrap_init()
+{
+    // set the real values up as soon as possible
+    REAL(malloc);
+    REAL(free);
+    REAL(calloc);
+    REAL(realloc);
+}
+#endif
diff --git a/wrap.h b/wrap.h
new file mode 100644
index 0000000..2053efd
--- /dev/null
+++ b/wrap.h
@@ -0,0 +1,21 @@
+#ifndef WRAP_H
+#define WRAP_H
+
+#include <dlfcn.h>
+
+#include "defines.h"
+
+#define _REAL(n) __real_##n
+#define REAL(n) \
+    ({ \
+        if (!_REAL(n)) \
+            _REAL(n) = dlsym(RTLD_NEXT, XSTR(n)); \
+        _REAL(n); \
+    })
+
+extern void *(*_REAL(malloc))(size_t size);
+extern void (*_REAL(free))(void *ptr);
+extern void *(*_REAL(calloc))(size_t nmemb, size_t size);
+extern void *(*_REAL(realloc))(void *ptr, size_t size);
+
+#endif /* WRAP_H */
-- 
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