Created simple C project with own libc.

test cases/ownstdlib/1 libc/libc.c

@@ -0,0 +1,35 @@
+/* Do not use this as the basis of your own libc.
+ * The code is probably unoptimal or wonky, as I
+ * had no prior experience with this, but instead
+ * just fiddled with the code until it worked.
+ */
+
+#include<stdio.h>
+
+#define STDOUT 1
+#define SYS_WRITE 4
+
+int simple_print(const char *msg, const long bufsize) {
+  int count;
+  long total_written = 0;
+  while(total_written < bufsize) {
+    asm(
+        "int $0x80\n\t"
+        : "=a"(count)
+        : "0"(SYS_WRITE), "b"(STDOUT), "c"(msg+total_written), "d"(bufsize-total_written)
+        :);
+    if(count == 0) {
+      return 1;
+    }
+    total_written += count;
+  }
+  return 0;
+}
+
+int simple_strlen(const char *str) {
+  int len = 0;
+  while(str[len] != '\0') {
+    len++;
+  }
+  return len;
+}

test cases/ownstdlib/1 libc/meson.build

@@ -0,0 +1,18 @@
+project('own libc', 'c')
+
+# A simple project that uses its own libc.
+
+# Start with manual flags to compile, then add platform support.
+
+libc = static_library('c', 'libc.c', 'stubstart.s',
+  c_args : '-nostdlib',
+  link_args : '-nostdlib',
+)
+
+exe = executable('selfcontained', 'prog.c',
+  c_args : '-nostdlib',
+  link_args : '-nostdlib',
+  link_with : libc,
+)
+
+test('standalone test', exe)

test cases/ownstdlib/1 libc/prog.c

@@ -0,0 +1,7 @@
+
+#include<stdio.h>
+
+int main() {
+  const char *message = "Hello without stdlib.\n";
+  return simple_print(message, simple_strlen(message));
+}

test cases/ownstdlib/1 libc/stdio.h

@@ -0,0 +1,5 @@
+#pragma once
+
+int simple_print(const char *msg, const long bufsize);
+
+int simple_strlen(const char *str);

test cases/ownstdlib/1 libc/stubstart.s

@@ -0,0 +1,8 @@
+.globl _start
+
+_start:
+
+    call main
+    movl %eax, %ebx
+    movl $1, %eax
+    int $0x80