source: trunk/essentials/sys-apps/gawk/test/getnr2tb.awk

#From vp@dmat.uevora.pt Thu Jun 18 09:10 EDT 1998
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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 }