Hi, this is a very straightforward fix for an undefined behavior in fortran/decl.c:
In the man page of sprintf, it's clearly state: === NOTES Some programs imprudently rely on code such as the following sprintf(buf, "%s some further text", buf); to append text to buf. However, the standards explicitly note that the results are undefined if source and destination buffers overlap when calling sprintf(), snprintf(), vsprintf(), and vsnprintf(). Depending on the version of gcc(1) used, and the compiler options employed, calls such as the above will not pro‐ duce the expected results. === in gcc/fortran/decl.c, there is exactly such case as following: 3361 sprintf (name, "%s_%d", name, kind_value); fixed it in this patch. bootstraped and tested on both X86 and Aarch64. no regression. Okay for trunk? thanks. Qing ==================================================== gcc/fortran/ChangeLog 2017-11-30 Qing Zhao <qing.z...@oracle.com <mailto:qing.z...@oracle.com>> * fortran/decl.c (gfc_get_pdt_instance): Adjust the call to sprintf to avoid the same buffer being both source and destination. --- gcc/fortran/decl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/gcc/fortran/decl.c b/gcc/fortran/decl.c index e57cfde..02dda24 100644 --- a/gcc/fortran/decl.c +++ b/gcc/fortran/decl.c @@ -3358,7 +3358,7 @@ gfc_get_pdt_instance (gfc_actual_arglist *param_list, gfc_symbol **sym, } gfc_extract_int (kind_expr, &kind_value); - sprintf (name, "%s_%d", name, kind_value); + sprintf (name + strlen (name), "_%d", kind_value); if (!name_seen && actual_param) actual_param = actual_param->next; -- 1.9.1