From 5c3049d2ef5d591dadd42bd074f4866616ef8231 Mon Sep 17 00:00:00 2001 From: Alan Modra Date: Mon, 20 Dec 2010 13:00:14 +0000 Subject: * 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. --- ld/ld.texinfo | 27 +++++++++++++-------------- 1 file changed, 13 insertions(+), 14 deletions(-) (limited to 'ld/ld.texinfo') diff --git a/ld/ld.texinfo b/ld/ld.texinfo index 6d36dfb..d4419aa 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 -- cgit v1.1