commit ec135c2cf41c8d681415b3b170e652421c8142a5
Author: Emil <emilwilliams@tuta.io>
Date:   Tue Sep 5 19:40:53 2023 -0600

    initial

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..38ae8bf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+*.so
+*.o
+plugin
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..518dd8e
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,17 @@
+#!/bin/make -f
+
+PREFIX := .
+
+CP := cp -f
+
+all: plug/libplug.so src/plugin
+
+plug/libplug.so:
+	make -C plug
+	$(CP) $@ $(PREFIX)
+
+src/plugin:
+	make -C src
+	$(CP) $@ $(PREFIX)
+
+.PHONY: all plug/libplug.so src/plugin
diff --git a/README b/README
new file mode 100644
index 0000000..4cad8e5
--- /dev/null
+++ b/README
@@ -0,0 +1,14 @@
+plug/ contains the dynamically loaded library,
+and of course, src/ has the core program.
+
+You'll have to use LD_LIBRARY_PATH='.' ./plugin
+This could be remedied with a little messing with
+get/setenv.
+
+There's a good reason for the fragmentation and
+recursion of the Makefiles, as how the files are
+compiled vary at compliation and link time
+(link-time not so applicable in this case, but
+ it is effected by CFLAGS anyways).
+
+Copy as you wish, credit not.
diff --git a/plug/Makefile b/plug/Makefile
new file mode 100644
index 0000000..6c827ae
--- /dev/null
+++ b/plug/Makefile
@@ -0,0 +1,6 @@
+include ../root.mk
+
+CFLAGS += -shared -fPIE
+
+libplug.so: plug.o
+	${LINK.c} $+ -o $@
diff --git a/plug/plug.c b/plug/plug.c
new file mode 100644
index 0000000..61e524d
--- /dev/null
+++ b/plug/plug.c
@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+void
+plug(void)
+{
+  printf("Plugin works.\n");
+}
diff --git a/plug/plug.h b/plug/plug.h
new file mode 100644
index 0000000..aaec119
--- /dev/null
+++ b/plug/plug.h
@@ -0,0 +1,10 @@
+#ifndef PLUG_H_
+
+#define BIND(lib, func, func_name) *(void **) (&func) = dlsym(lib, func_name)
+
+typedef void (*plug_t)(void);
+
+static plug_t plug;
+
+#define PLUG_H_
+#endif
diff --git a/root.mk b/root.mk
new file mode 100644
index 0000000..1c92c3f
--- /dev/null
+++ b/root.mk
@@ -0,0 +1,6 @@
+CFLAGS   := -std=c89 -Wall -Wextra -Wpedantic -Wshadow -Wundef
+CPPFLAGS := -D_FORTIFY_SOURCE=2
+LDLIBS   := -lplug
+
+.c.o:
+	${COMPILE.c} $< -o $@
diff --git a/src/Makefile b/src/Makefile
new file mode 100644
index 0000000..72d7624
--- /dev/null
+++ b/src/Makefile
@@ -0,0 +1,6 @@
+include ../root.mk
+
+CPPFLAGS += -I../plug -L../plug
+
+plugin: main.o
+	${LINK.c} $+ -o $@ ${LDLIBS}
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..2330b9c
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,31 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <dlfcn.h>
+
+#include "plug.h"
+
+int
+main (void)
+{
+  int x = 0;
+  char * libplug_fn = "libplug.so";
+  void * libplug = NULL;
+  while (1)
+  {
+    if (libplug) { dlclose(libplug); }
+    libplug = dlopen(libplug_fn, RTLD_NOW);
+    BIND(libplug, plug, "plug");
+    if (!libplug)
+    { fprintf(stderr, "ERR: Cannot load dynamic library %s: %s\n", libplug_fn, dlerror()); }
+    else
+    {
+      *(void **) (&plug) = dlsym(libplug, "plug");
+      printf("frame %d: ", x++);
+      if (plug)
+      { plug(); }
+      else
+      { fprintf(stderr, "ERR: Cannot find %s symbol in %s: %s\n", "plug", libplug_fn, dlerror()); }
+    }
+    sleep(2);
+  }
+}