Added embeding notes

1 files changed, 190 insertions, 6 deletions

diff --git a/md/notes/undefined_c/titles.md b/md/notes/undefined_c/titles.md
index 4e7361e..18fcdec 100644
--- a/md/notes/undefined_c/titles.md
+++ b/md/notes/undefined_c/titles.md
@@ -1,4 +1,4 @@
-title:Undefine C 
+title:Undefined C 
 keywords:c,linux,asm 
 
 # Undefined C
@@ -1426,30 +1426,209 @@ undefined_b.c:5:14: runtime error: division by zero
 fish: Job 1, './undefined_b' terminated by signal SIGFPE (Floating point exception)
 ```
 
-
+<!--
 ### FARMA-C
-
+--->
 
 
 
 
 ### Write plugins
-
-
 ### Preload library
 
 
 ## Embedding C
 
+Most of the programming languages support embeding C. As C language have where simple
+functiong naming when its mangled to object format it makes it easy target when 
+linking with other languages. Most of other languages have incompatible naming for
+functions when compiled to binary. 
+
 ### Embed in C++
+
+__lib.h__
+```c
+#include <stdlib.h>
+#include <stdio.h>
+
+int fun_secret_1();
+```
+
+__lib.c__
+```c
+#include "lib.h"
+
+int fun_secret_1() {
+	printf("Hello from C\n");
+	return -1;
+}
+```
+
+First thing to notice is when file is compiled with C++ is that the name of the function are in different format
+then when its compiled with C. 
+```
+$ g++ -c lib.c
+$ readelf -s lib.o
+Symbol table '.symtab' contains 6 entries:
+   Num:    Value          Size Type    Bind   Vis      Ndx Name
+     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
+     1: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS lib.c
+     2: 0000000000000000     0 SECTION LOCAL  DEFAULT    1 .text
+     3: 0000000000000000     0 SECTION LOCAL  DEFAULT    5 .rodata
+     4: 0000000000000000    26 FUNC    GLOBAL DEFAULT    1 _Z12fun_secret_1v
+     5: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT  UND puts
+
+```
+
+Lets tell C++ that file is C language by adding **extern "c"**
+
+__lib.h__
+```c
+#include <stdlib.h>
+#include <stdio.h>
+
+extern "C" {
+
+int fun_secret_1();
+
+}
+```
+
+__lib.c__
+```c
+#include "lib.h"
+
+extern "C" {
+
+int fun_secret_1() {
+	printf("Hello from C\n");
+	return -1;
+}
+
+}
+```
+
+Now compiled object file have C function names. 
+
+```
+$ g++ lib.c -c
+$ readelf -s lib.o
+
+Symbol table '.symtab' contains 6 entries:
+   Num:    Value          Size Type    Bind   Vis      Ndx Name
+     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
+     1: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS lib.c
+     2: 0000000000000000     0 SECTION LOCAL  DEFAULT    1 .text
+     3: 0000000000000000     0 SECTION LOCAL  DEFAULT    5 .rodata
+     4: 0000000000000000    26 FUNC    GLOBAL DEFAULT    1 fun_secret_1
+     5: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT  UND puts
+
+```
+
+__cppembed.cpp___
+```cpp
+#include "lib.h"
+
+int main() {
+	fun_secret_1();
+}
+```
+
+Doing oposite way running C++ from C  
+[/writeup/wraping_c_plus_plus_exceptions_templates_and_classes_in_c.md](/writeup/wraping_c_plus_plus_exceptions_templates_and_classes_in_c.md)
+
 ### Embed in Go
+
+__lib.h__
+```c
+#include <stdlib.h>
+#include <stdio.h>
+
+int fun_secret_1();
+```
+__lib.c__
+```c
+#include "lib.h"
+
+int fun_secret_1() {
+	printf("Hello from C\n");
+	return -1;
+}
+```
+
+__main.go__
+```go
+package main
+// #cgo CFLAGS: -g -Wall
+// #include <stdlib.h>
+// #include "lib.h"
+import "C"
+import (
+	"fmt"
+	
+)
+func main() {
+	fmt.Println("Start program")
+	C.fun_secret_1()
+	fmt.Println("End program")
+}
+```
+
+```
+go build
+```
+
+[https://karthikkaranth.me/blog/calling-c-code-from-go/](https://karthikkaranth.me/blog/calling-c-code-from-go/)
+
+
 ### Embed in Swift
-### Embed in JS
+
+[/writeup/linux_hello_world_in_swift.md](/writeup/linux_hello_world_in_swift.md)
+
+### Embed in Rust
+
+__lib.c__
+```c
+#include <stdio.h>
+#include <stdlib.h>
+
+int fun_secret_1() {
+	printf("Hello from C\n");
+	return -1;
+}
+```
+
+```rust
+extern "C" {
+	fn fun_secret_1();
+}
+
+//rustc main.rs -o hello
+fn main() {
+	println!("Start program");
+	unsafe {fun_secret_1()}
+	println!("End program");
+}
+```
+
+Compile with
+
+```
+gcc -c lib.c
+gcc -shared lib.o -o liblib.so
+rustc main.rs -l lib -L . -o hello -C link-arg="-Wl,-rpath=./"
+```
+
+[https://dev.to/xphoniex/how-to-call-c-code-from-rust-56do](https://dev.to/xphoniex/how-to-call-c-code-from-rust-56do)
 
 ### Lua in C
+
+[/writeup/embedding_lua_in_c.md](/writeup/embedding_lua_in_c.md)  
+
 ### Python in C
 
 
+
 ## Multiplatform
 
 ### Cross compile
@@ -1459,6 +1638,11 @@ fish: Job 1, './undefined_b' terminated by signal SIGFPE (Floating point excepti
 ### AVR8
 ### Emscripten
 
+[/writeup/web_assembly_sdl_example.md](/writeup/web_assembly_sdl_example.md)
+
+#### Embed in JS
+
+
 
 ## Graphics