Re: [PATCH] Fix unsafe function attributes for special functions (PR 71876)

[Bernd Edlinger <bernd dot edlinger at hotmail dot de>]

Hi,

based on the discussion here, I have updated my patch again...

This is the rest of the patch, which removes outdated function names,
and creates built-in definitions for vfork, getcontext, savectx.
These built-ins have the return_twice attribute but not the
leaf attribute, because we do not really know, what these functions
do.

The reason for ceating the builtin functions is, that I would like
to get a warning about conflicting builtin definition if someone
accidentally picks the name of one of these less well known special
functions, which are _not_ reserved names in most environments.

I do not define builtins (without __builtin_ prefix) for setjmp and
sigsetjmp because these are like wildcards, and they fall in the
well-known category anyways.

I still retain the handling of these functions in special_function_p
because even in a free standing environment, returning
ECF_RETURNS_TWICE is on the safe side.



Is it OK for trunk after boot-strap and regression-testing?


Thanks
Bernd.

Attachment: changelog-pr71876.txt
Description: changelog-pr71876.txt

Index: gcc/builtin-attrs.def
===================================================================
--- gcc/builtin-attrs.def	(revision 238611)
+++ gcc/builtin-attrs.def	(working copy)
@@ -131,6 +131,8 @@ DEF_ATTR_TREE_LIST (ATTR_NORETURN_NOTHROW_LIST, AT
 			ATTR_NULL, ATTR_NOTHROW_LIST)
 DEF_ATTR_TREE_LIST (ATTR_NORETURN_NOTHROW_LEAF_LIST, ATTR_NORETURN,\
 			ATTR_NULL, ATTR_NOTHROW_LEAF_LIST)
+DEF_ATTR_TREE_LIST (ATTR_RT_NOTHROW_LIST, ATTR_RETURNS_TWICE,\
+			ATTR_NULL, ATTR_NOTHROW_LIST)
 DEF_ATTR_TREE_LIST (ATTR_RT_NOTHROW_LEAF_LIST, ATTR_RETURNS_TWICE,\
 			ATTR_NULL, ATTR_NOTHROW_LEAF_LIST)
 DEF_ATTR_TREE_LIST (ATTR_COLD_NOTHROW_LEAF_LIST, ATTR_COLD,\
Index: gcc/builtins.def
===================================================================
--- gcc/builtins.def	(revision 238611)
+++ gcc/builtins.def	(working copy)
@@ -796,6 +796,7 @@ DEF_EXT_LIB_BUILTIN    (BUILT_IN_FINITED32, "finit
 DEF_EXT_LIB_BUILTIN    (BUILT_IN_FINITED64, "finited64", BT_FN_INT_DFLOAT64, ATTR_CONST_NOTHROW_LEAF_LIST)
 DEF_EXT_LIB_BUILTIN    (BUILT_IN_FINITED128, "finited128", BT_FN_INT_DFLOAT128, ATTR_CONST_NOTHROW_LEAF_LIST)
 DEF_GCC_BUILTIN        (BUILT_IN_FPCLASSIFY, "fpclassify", BT_FN_INT_INT_INT_INT_INT_INT_VAR, ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
+DEF_EXT_LIB_BUILTIN    (BUILT_IN_GETCONTEXT, "getcontext", BT_FN_INT_PTR, ATTR_RT_NOTHROW_LIST)
 DEF_GCC_BUILTIN        (BUILT_IN_ISFINITE, "isfinite", BT_FN_INT_VAR, ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
 DEF_GCC_BUILTIN        (BUILT_IN_ISINF_SIGN, "isinf_sign", BT_FN_INT_VAR, ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
 DEF_C99_C90RES_BUILTIN (BUILT_IN_ISINF, "isinf", BT_FN_INT_VAR, ATTR_CONST_NOTHROW_TYPEGENERIC)
@@ -836,6 +837,7 @@ DEF_GCC_BUILTIN        (BUILT_IN_PREFETCH, "prefet
 DEF_LIB_BUILTIN        (BUILT_IN_REALLOC, "realloc", BT_FN_PTR_PTR_SIZE, ATTR_NOTHROW_LEAF_LIST)
 DEF_GCC_BUILTIN        (BUILT_IN_RETURN, "return", BT_FN_VOID_PTR, ATTR_NORETURN_NOTHROW_LEAF_LIST)
 DEF_GCC_BUILTIN        (BUILT_IN_RETURN_ADDRESS, "return_address", BT_FN_PTR_UINT, ATTR_LEAF_LIST)
+DEF_EXT_LIB_BUILTIN    (BUILT_IN_SAVECTX, "savectx", BT_FN_VOID_PTR, ATTR_RT_NOTHROW_LIST)
 DEF_GCC_BUILTIN        (BUILT_IN_SAVEREGS, "saveregs", BT_FN_PTR_VAR, ATTR_NULL)
 DEF_GCC_BUILTIN        (BUILT_IN_SETJMP, "setjmp", BT_FN_INT_PTR, ATTR_RT_NOTHROW_LEAF_LIST)
 DEF_EXT_LIB_BUILTIN    (BUILT_IN_STRFMON, "strfmon", BT_FN_SSIZE_STRING_SIZE_CONST_STRING_VAR, ATTR_FORMAT_STRFMON_NOTHROW_3_4)
@@ -849,6 +851,7 @@ DEF_GCC_BUILTIN        (BUILT_IN_VA_END, "va_end",
 DEF_GCC_BUILTIN        (BUILT_IN_VA_START, "va_start", BT_FN_VOID_VALIST_REF_VAR, ATTR_NOTHROW_LEAF_LIST)
 DEF_GCC_BUILTIN        (BUILT_IN_VA_ARG_PACK, "va_arg_pack", BT_FN_INT, ATTR_PURE_NOTHROW_LEAF_LIST)
 DEF_GCC_BUILTIN        (BUILT_IN_VA_ARG_PACK_LEN, "va_arg_pack_len", BT_FN_INT, ATTR_PURE_NOTHROW_LEAF_LIST)
+DEF_EXT_LIB_BUILTIN    (BUILT_IN_VFORK, "vfork", BT_FN_PID, ATTR_RT_NOTHROW_LIST)
 DEF_EXT_LIB_BUILTIN    (BUILT_IN__EXIT, "_exit", BT_FN_VOID_INT, ATTR_NORETURN_NOTHROW_LEAF_LIST)
 DEF_C99_BUILTIN        (BUILT_IN__EXIT2, "_Exit", BT_FN_VOID_INT, ATTR_NORETURN_NOTHROW_LEAF_LIST)
 
Index: gcc/calls.c
===================================================================
--- gcc/calls.c	(revision 238611)
+++ gcc/calls.c	(working copy)
@@ -474,8 +474,6 @@ emit_call_1 (rtx funexp, tree fntree ATTRIBUTE_UNU
    For example, if the function might return more than one time (setjmp), then
    set RETURNS_TWICE to a nonzero value.
 
-   Similarly set NORETURN if the function is in the longjmp family.
-
    Set MAY_BE_ALLOCA for any memory allocation function that might allocate
    space from the stack such as alloca.  */
 
@@ -491,7 +489,7 @@ special_function_p (const_tree fndecl, int flags)
     name_decl = DECL_NAME (cgraph_node::get (fndecl)->orig_decl);
 
   if (fndecl && name_decl
-      && IDENTIFIER_LENGTH (name_decl) <= 17
+      && IDENTIFIER_LENGTH (name_decl) <= 11
       /* Exclude functions not at the file scope, or not `extern',
 	 since they are not the magic functions we would otherwise
 	 think they are.
@@ -514,43 +512,22 @@ special_function_p (const_tree fndecl, int flags)
 	  && ! strcmp (name, "alloca"))
 	flags |= ECF_MAY_BE_ALLOCA;
 
-      /* Disregard prefix _, __ or __x.  */
+      /* Disregard prefix _ or __.  */
       if (name[0] == '_')
 	{
-	  if (name[1] == '_' && name[2] == 'x')
-	    tname += 3;
-	  else if (name[1] == '_')
+	  if (name[1] == '_')
 	    tname += 2;
 	  else
 	    tname += 1;
 	}
 
-      if (tname[0] == 's')
-	{
-	  if ((tname[1] == 'e'
-	       && (! strcmp (tname, "setjmp")
-		   || ! strcmp (tname, "setjmp_syscall")))
-	      || (tname[1] == 'i'
-		  && ! strcmp (tname, "sigsetjmp"))
-	      || (tname[1] == 'a'
-		  && ! strcmp (tname, "savectx")))
-	    flags |= ECF_RETURNS_TWICE | ECF_LEAF;
-
-	  if (tname[1] == 'i'
-	      && ! strcmp (tname, "siglongjmp"))
-	    flags |= ECF_NORETURN;
-	}
-      else if ((tname[0] == 'q' && tname[1] == 's'
-		&& ! strcmp (tname, "qsetjmp"))
-	       || (tname[0] == 'v' && tname[1] == 'f'
-		   && ! strcmp (tname, "vfork"))
-	       || (tname[0] == 'g' && tname[1] == 'e'
-		   && !strcmp (tname, "getcontext")))
-	flags |= ECF_RETURNS_TWICE | ECF_LEAF;
-
-      else if (tname[0] == 'l' && tname[1] == 'o'
-	       && ! strcmp (tname, "longjmp"))
-	flags |= ECF_NORETURN;
+      /* ECF_RETURNS_TWICE is safe even for -ffreestanding.  */
+      if (! strcmp (tname, "setjmp")
+	  || ! strcmp (tname, "sigsetjmp")
+	  || ! strcmp (name, "savectx")
+	  || ! strcmp (name, "vfork")
+	  || ! strcmp (name, "getcontext"))
+	flags |= ECF_RETURNS_TWICE;
     }
 
   if (DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL)