From 476d1f5deaf8a2982256d0d978a3ce99ae68723e Mon Sep 17 00:00:00 2001
From: FreeArtMan <dos21h@gmail.com>
Date: Fri, 12 Aug 2022 11:33:09 +0100
Subject: Add static

---
 md/notes/undefined_c/titles.md | 85 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)

(limited to 'md')

diff --git a/md/notes/undefined_c/titles.md b/md/notes/undefined_c/titles.md
index 014035b..158ed20 100644
--- a/md/notes/undefined_c/titles.md
+++ b/md/notes/undefined_c/titles.md
@@ -454,6 +454,7 @@ int main()
 #include <stdio.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include <stdint.h>
 
 int main() {
 	int arr[4] = {0x00112233,0x44556677,0x8899AABB, 0xCCDDEEFF};
@@ -509,12 +510,96 @@ $ hexdump int.bin2
 Compiler have whole list of command line arguments that you can enable for different purposes, lets look into some of them
 https://gcc.gnu.org/onlinedocs/gcc/Option-Summary.html
 
+Lets try to apply some of the flags to examples above.
+
+Best starte options is, those will give you more warnings.
 
+```
+-Wall -Wextra
+```
+
+Most of the examples here was written in sloppy style, so adding extra checks like will find more issues with code, probably
+all of provided examples will show issues with this extra compiler flags
+
+```
+Wformat-security -Wduplicated-cond -Wfloat-equal -Wshadow -Wconversion -Wjump-misses-init -Wlogical-not-parentheses -Wnull-dereference
+```
+
+To get all macroses expanded in C code add compiler flag. Output will be C source with all macro expansion
+```
+-E
+```
+
+Output resulting file not to binary but to generated assembly add
+```
+-S
+```
+
+More readable output can be obtained with
+
+```
+gcc FILE.c -Wa,-adhln=FILE.S -g -fverbose-asm -masm=intel
+```
+
+Basic compiler optimisation flags that can speedup program or make it smaller
+
+```
+-O  -O0  -O1  -O2  -O3  -Os  -Ofast  -Og  -Oz
+```
+
+https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#Optimize-Options
+
+https://panthema.net/2013/0124-GCC-Output-Assembler-Code/  
+https://blogs.oracle.com/linux/post/making-code-more-secure-with-gcc-part-1  
 
 
 ### Static binary
+
+Static binary don't use any shared libraries, and its possible to built it once and distribute on other platforms
+without need to install dependencies. 
+
+
+```c
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char **argv) {
+	return 0;
+}
+```
+
+First step to compile file and see that is dynamically lined
+```
+$ gcc static_elf.c -o static_elf
+$ file static_elf
+static_elf: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=bc6ac706075874858e1c4a8accf77e704f4ea25a, for GNU/Linux 4.4.0, with debug_info, not stripped
+$ ldd ./static_elf
+	linux-vdso.so.1 (0x00007ffccef49000)
+	libc.so.6 => /usr/lib/libc.so.6 (0x00007fcbb8800000)
+	/lib64/ld-linux-x86-64.so.2 => /usr/lib64/ld-linux-x86-64.so.2 (0x00007fcbb8b63000)
+
+```
+
+After adding static option we can verify that tools now report it as statically linked. Size of binary increased as all functions
+that require to run executable are now contained in binary.
+
+```
+$ gcc static_elf.c -static -o static_elf
+$ file static_elf
+static_elf: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, BuildID[sha1]=c54d2e4d2a3d11fe920bee9a44af045c6f67ab56, for GNU/Linux 4.4.0, with debug_info, not stripped
+$ ldd static_elf 
+	not a dynamic executable
+```
+
+Statically compiled file should work on most platforms.
+
 ### Dynamic binary
+
+
+
 ### stdin,stdout,stderr
+
+
 ### Styles
 
 
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