gcc 15 and C23 force some union trickery on buffer.h :-(

add a few buffer_init*_forread variants to pretend we have type safety
  make sure buffer_init_staticcontents handles flushing attempts

buffer/buffer_init_staticcontents.c

@@ -1,14 +1,28 @@
 #include <libowfat/buffer.h>
+#include <errno.h>
 
-static ssize_t op() {
+static ssize_t op(int fd,const void* buf,size_t l) {
+  (void)fd;
+  (void)buf;
+  (void)l;
+  errno=ENOENT;
   return 0;
 }
 
 void buffer_init_staticcontents(buffer* b, char* y, size_t len) {
   b->x=y;
-  b->p=0; b->a=b->n=len;
+  b->p=0; b->a=len; b->n=0;
   b->fd=-1;
-  b->op=op;
+  b->op.wop=op;
+  b->deinit=0;
+}
+
+void buffer_init_staticcontents_forread(buffer* b, const char* y, size_t len) {
+  b->x=(char*)y;
+  b->p=0;
+  b->a=b->n=len;
+  b->fd=-1;
+  b->op.wop=op;
   b->deinit=0;
 }
 
@@ -26,7 +40,7 @@ void buffer_init_staticcontents(buffer* b, char* y, size_t len) {
 
 int main() {
   buffer b;
-  buffer_init_staticcontents(&b, "fnord", 5);
+  buffer_init_staticcontents_forread(&b, "fnord", 5);
   char tmp[6];
   assert(buffer_get(&b, tmp, 6) == 5);
   assert(!memcmp(tmp,"fnord",5));