- if ((gz = gzdopen(fd, "rb")) == NULL)
- err((int)MANDOCLEVEL_SYSERR, "%s", file);
+ /*
+ * Duplicating the file descriptor is required
+ * because we will have to call gzclose(3)
+ * to free memory used internally by zlib,
+ * but that will also close the file descriptor,
+ * which this function must not do.
+ */
+ if ((fd = dup(fd)) == -1) {
+ mandoc_vmsg(MANDOCERR_FILE, curp, 0, 0,
+ "dup: %s", strerror(errno));
+ return 0;
+ }
+ if ((gz = gzdopen(fd, "rb")) == NULL) {
+ mandoc_vmsg(MANDOCERR_FILE, curp, 0, 0,
+ "gzdopen: %s", strerror(errno));
+ close(fd);
+ return 0;
+ }