* ld.texinfo (Expression Section): Describe treatment of numbers

	and absolute symbols.
	* ldemul.c (after_open_default): Look up __ld_compatibility.
	* ldexp.c (fold_name): Convert absolute symbols to numbers when
	inside output section definitions, or when __ld_compatibility >= 221.
	(exp_fold_tree_1): Convert numbers to absolute when not in output
	section definition and __ld_compatibility < 221.  Don't always
	convert values outside an output section definition to absolute.
	* ldexp.h (uses_defined): Comment.
	* ldlang.c (ld_compatibility): New variable.
	* ldlang.h (ld_compatibility): Declare.
	* emultempl/aix.em, * emultempl/armcoff.em, * emultempl/beos.em,
	* emultempl/elf32.em, * emultempl/genelf.em, * emultempl/lnk960.em,
	* emultempl/m68kcoff.em, * emultempl/mmo.em, * emultempl/pe.em,
	* emultempl/pep.em, * emultempl/sunos.em, * emultempl/z80.em: Call
	after_open_default from after_open function.

1 files changed, 13 insertions, 14 deletions

diff --git a/ld/ld.texinfo b/ld/ld.texinfo
index 6d36dfb63d..d4419aa5b5 100644
--- a/ld/ld.texinfo
+++ b/ld/ld.texinfo
@@ -5503,17 +5503,17 @@ section relative symbols and for builtin functions that return an
 address, such as @code{ADDR}, @code{LOADADDR}, @code{ORIGIN} and
 @code{SEGMENT_START}.  Other terms are simply numbers, or are builtin
 functions that return a non-address value, such as @code{LENGTH}.
-
-When the linker evaluates an expression, the result depends on where
-the expression is located in a linker script.  Expressions appearing
-outside an output section definitions are evaluated with all terms
-first being converted to absolute addresses before applying operators,
-and evaluate to an absolute address result.  Expressions appearing
-inside an output section definition are evaluated with more complex
-rules, but the aim is to treat terms as relative addresses and produce
-a relative address result.  In particular, an assignment of a number
-to a symbol results in a symbol relative to the output section with an
-offset given by the number.  So, in the following simple example,
+One complication is that unless you assign @code{__ld_compatibility}
+a value of 221 or larger, numbers and absolute symbols are treated
+differently depending on their location, for compatibility with older
+versions of @code{ld}.  Expressions appearing outside an output
+section definition treat all numbers as absolute addresses.
+Expressions appearing inside an output section definition treat
+absolute symbols as numbers.  If @code{__ld_compatibility} is assigned
+a value larger than 221, then absolute symbols and numbers are simply
+treated as numbers everywhere.
+
+In the following simple example,
 
 @smallexample
 @group
@@ -5537,9 +5537,8 @@ address 0x100 in the first two assignments, then both @code{.} and
 @code{__data_start} are set to 0x10 relative to the @code{.data}
 section in the second two assignments.
 
-For expressions appearing inside an output section definition
-involving numbers, relative addresses and absolute addresses, ld
-follows these rules to evaluate terms:
+For expressions involving numbers, relative addresses and absolute
+addresses, ld follows these rules to evaluate terms:
 
 @itemize @bullet
 @item