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#To: arnold@gnu.org

#Subject: concatenation bug in gawk 3.0.3

#Date: Thu, 18 Jun 1998 14:13:57 +0200

#From: Vasco Pedro <vp@dmat.uevora.pt>

#Content-Type: text

#Content-Length: 2285

#Status: RO

#

#Hi,

#

#The gawk program '{print NR " " 10/NR}' will print:

#

#1 10

#5 5

#3 3.33333

#2 2.5

#2 2

#1 1.66667

#

#instead of the correct:

#

#1 10

#2 5

#3 3.33333

#4 2.5

#5 2

#6 1.66667

#

#You'll notice, on the incorrect output, that the first column is

#the first digit of the second.

#

#I think the problem comes from the way builtin variables are handled.

#Since the items to be concatenated are processed in reverse order and

#the return value of tree_eval(``NR'') is a pointer to the value part

#of `NR_node', the `unref()' of `NR_node' due to its second occurrence

#will leave a dangling pointer in `strlist'. The reason that it doesn't

#reuse the freed space with objects of the same type. (Using Electric

#Fence with EF_PROTECT_FREE set confirms that freed space is being

#accessed.)

#

#The enclosed patch (hack would be a better word to describe it) is

#all I could come up with. With it installed, things seem to work ok,

#but I doubt this is the correct way to do it. (If I treated the

#case for `Node_field_spec' as the I did others, `make check' would

#fail in several places.)

#

#Regards,

#vasco

#

#*** eval.c~	Tue May  6 21:39:55 1997

#--- eval.c	Thu Jun 18 13:39:25 1998

#***************

#*** 685,697 ****

#  		return func_call(tree->rnode, tree->lnode);

#  

#  		/* unary operations */

#  	case Node_NR:

#  	case Node_FNR:

#  	case Node_NF:

#  	case Node_FIELDWIDTHS:

#  	case Node_FS:

#  	case Node_RS:

#- 	case Node_field_spec:

#  	case Node_subscript:

#  	case Node_IGNORECASE:

#  	case Node_OFS:

#--- 685,700 ----

#  		return func_call(tree->rnode, tree->lnode);

#  

#  		/* unary operations */

#+ 	case Node_field_spec:

#+ 		lhs = get_lhs(tree, (Func_ptr *) NULL);

#+ 		return *lhs;

#+ 

#  	case Node_NR:

#  	case Node_FNR:

#  	case Node_NF:

#  	case Node_FIELDWIDTHS:

#  	case Node_FS:

#  	case Node_RS:

#  	case Node_subscript:

#  	case Node_IGNORECASE:

#  	case Node_OFS:

#***************

#*** 699,705 ****

#  	case Node_OFMT:

#  	case Node_CONVFMT:

#  		lhs = get_lhs(tree, (Func_ptr *) NULL);

#! 		return *lhs;

#  

#  	case Node_var_array:

#  		fatal("attempt to use array `%s' in a scalar context",

#--- 702,710 ----

#  	case Node_OFMT:

#  	case Node_CONVFMT:

#  		lhs = get_lhs(tree, (Func_ptr *) NULL);

#! 		r = dupnode(*lhs);

#! 		r->flags |= TEMP;

#! 		return r;

#  

#  	case Node_var_array:

#  		fatal("attempt to use array `%s' in a scalar context",

#

{ print NR " " 10/NR }