update fixture

Author: emberian

src/ch04-symbol-tables.md

@@ -259,14 +259,11 @@ A symbol with global binding should be defined exactly once (across all input fi
 
 ```bash
 $ gcc -c file1.c -o file1.o  # defines 'foo'
-cc1: fatal error: file1.c: No such file or directory
-compilation terminated.
 $ gcc -c file2.c -o file2.o  # also defines 'foo'
-cc1: fatal error: file2.c: No such file or directory
-compilation terminated.
 $ gcc file1.o file2.o -o out
-/usr/bin/ld: cannot find file1.o: No such file or directory
-/usr/bin/ld: cannot find file2.o: No such file or directory
+/usr/bin/ld: file2.o:(.data+0x0): multiple definition of `foo'; file1.o:(.data+0x0): first defined here
+/usr/bin/ld: /lib/aarch64-linux-gnu/crt1.o: in function `__wrap_main':
+(.text+0x38): undefined reference to `main'
 collect2: error: ld returned 1 exit status
 ```
 

src/ch06-static-linking.md

@@ -180,12 +180,12 @@ This is **selective linking**—you don't pay for what you don't use.
 
 ```bash
 $ ar -t libc.a | wc -l
-0
+2021
 $ nm hello | grep ' T ' | wc -l
-0
+5
 ```
 
-The library has 1552 object files, but only ~42 functions end up in your hello world. The rest are discarded.
+The library has ~2000 object files, but only a handful of functions end up in your hello world. The rest are discarded.
 
 ### Link Order Matters
 

src/ch07-dynamic-linking.md

@@ -43,7 +43,7 @@ libmath.so: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV),
 dynamically linked, not stripped
 
 $ readelf -h libmath.so | grep Type
-readelf: Error: 'libmath.so': No such file
+  Type:                              DYN (Shared object file)
 ```
 
 Type `DYN` (not `EXEC`). It has:

tools/mdbook-exec/src/main.rs

@@ -117,11 +117,37 @@ cat > simple.c << 'FIXTURE_EOF'
 int main() { return 42; }
 FIXTURE_EOF
 
+# For ch04 - demonstrating multiple definition errors
+cat > file1.c << 'FIXTURE_EOF'
+int foo = 1;
+FIXTURE_EOF
+
+cat > file2.c << 'FIXTURE_EOF'
+int foo = 2;
+FIXTURE_EOF
+
+# Compile object files
 gcc -c math.c -o math.o
 gcc -c main.c -o main.o
 gcc main.o math.o -o program
 gcc -c simple.c -o simple.o
 gcc simple.c -o simple
+
+# For ch07 - shared library example
+gcc -fPIC -shared math.c -o libmath.so
+
+# For ch06 - static linking examples  
+cat > hello.c << 'FIXTURE_EOF'
+#include <stdio.h>
+int main() { printf("Hello, world!\n"); return 0; }
+FIXTURE_EOF
+gcc hello.c -o hello
+
+# Create symlink for libc.a if it exists (location varies by distro)
+LIBC_PATH=$(find /usr/lib -name 'libc.a' 2>/dev/null | head -1)
+if [ -n "$LIBC_PATH" ]; then
+    ln -sf "$LIBC_PATH" libc.a
+fi
 "#;
 
         let output = Command::new("docker")