Data commit

Task/Call-a-function-in-a-shared-library/C/call-a-function-in-a-shared-library-1.c

@@ -0,0 +1,36 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <dlfcn.h>
+
+int myopenimage(const char *in)
+{
+  static int handle=0;
+  fprintf(stderr, "internal openimage opens %s...\n", in);
+  return handle++;
+}
+
+int main()
+{
+  void *imglib;
+  int (*extopenimage)(const char *);
+  int imghandle;
+
+  imglib = dlopen("./fakeimglib.so", RTLD_LAZY);
+  if ( imglib != NULL ) {
+    /* extopenimage = (int (*)(const char *))dlsym(imglib,...)
+       "man dlopen" says that C99 standard leaves casting from
+       "void *" to a function pointer undefined. The following is the
+       POSIX.1-2003 workaround found in man */
+    *(void **)(&extopenimage) = dlsym(imglib, "openimage");
+    /* the following works with gcc, gives no warning even with
+       -Wall -std=c99 -pedantic options... :D */
+    /* extopenimage = dlsym(imglib, "openimage"); */
+    imghandle = extopenimage("fake.img");
+  } else {
+    imghandle = myopenimage("fake.img");
+  }
+  printf("opened with handle %d\n", imghandle);
+  /* ... */
+  if (imglib != NULL ) dlclose(imglib);
+  return EXIT_SUCCESS;
+}

Task/Call-a-function-in-a-shared-library/C/call-a-function-in-a-shared-library-2.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+/* gcc -shared -nostartfiles fakeimglib.c -o fakeimglib.so */
+int openimage(const char *s)
+{
+  static int handle = 100;
+  fprintf(stderr, "opening %s\n", s);
+  return handle++;
+}