compress: compressor: check that function ctx size is >0 before returning a pointer to it

compress/compressor.c

@@ -2,6 +2,7 @@
 
 #include "function.h"
 
+#include <assert.h>
 #include <blue/compress/compressor.h>
 #include <blue/core/ringbuffer.h>
 #include <stdlib.h>
@@ -137,6 +138,7 @@ bool b_compressor_eof(const struct b_compressor *compressor)
 
 void *b_compressor_get_function_ctx(struct b_compressor *compressor)
 {
+	assert(compressor->c_func->f_buffer_size > 0);
 	unsigned char *p = (unsigned char *)compressor;
 	p += sizeof *compressor;
 	return p;