From f5f7251972748d76f9f6e0cacdcae97a303a02dc Mon Sep 17 00:00:00 2001
From: Sunil Nimmagadda <sunil@nimmagadda.net>
Date: Sat, 24 Oct 2026 16:28:16 +0530
Subject: Segments: normalize and validate.

While here mark mandatory and optional fields.
---
 elf/segment.lua | 36 +++++++++++++++++++++++++++++-------
 mkelf.lua       |  6 +++++-
 sample.elf.lua  |  7 -------
 3 files changed, 34 insertions(+), 15 deletions(-)

diff --git a/elf/segment.lua b/elf/segment.lua
index 662f42e..19cb6d0 100644
--- a/elf/segment.lua
+++ b/elf/segment.lua
@@ -3,17 +3,39 @@ local fmt = require("elf.fmt")
 
 ---@class Segment
 ---@field type SegmentType
----@field flags integer
----@field offset integer
----@field vaddr integer
----@field paddr integer
----@field filesz integer
----@field memsz integer
----@field align integer
+---@field flags? integer
+---@field offset? integer
+---@field vaddr? integer
+---@field paddr? integer
+---@field filesz? integer
+---@field memsz? integer
+---@field align? integer
+---@field first_section? string
+---@field last_section? string
 
 ---@class Segments
 local M = {}
 
+
+function M.normalize(phdrs)
+    for _, phdr in ipairs(phdrs) do
+        phdr.flags = phdr.flags or 0
+        phdr.offset = phdr.offset or 0
+        phdr.vaddr = phdr.vaddr or 0
+        phdr.paddr = phdr.paddr or 0
+        phdr.filesz = phdr.filesz or 0
+        phdr.memsz = phdr.memsz or 0
+        phdr.align = phdr.align or 1
+    end
+end
+
+function M.validate(phdrs)
+    for _, phdr in ipairs(phdrs) do
+        if not phdr.type then error("type is required in segment", 3) end
+        -- TODO additional validations
+    end
+end
+
 ---@param phdr Segment
 ---@param endian Endian
 ---@return string
diff --git a/mkelf.lua b/mkelf.lua
index d6e412c..f078764 100644
--- a/mkelf.lua
+++ b/mkelf.lua
@@ -34,7 +34,11 @@ local function loadconfig(fn)
                 t:normalize()
                 t:validate()
             end,
-            segments = function(t) segments = setmetatable(t, segments_mt) end,
+            segments = function(t)
+                segments = setmetatable(t, segments_mt)
+                t:normalize()
+                t:validate()
+            end,
             sections = function(t) sections = setmetatable(t, sections_mt) end,
         },
         __newindex = function(_, name)
diff --git a/sample.elf.lua b/sample.elf.lua
index d37a7c5..5b3c12a 100644
--- a/sample.elf.lua
+++ b/sample.elf.lua
@@ -8,13 +8,6 @@ header {
 segments {
     {
         type = SegmentType.dynamic,
-        flags = SegmentFlags.x,
-        offset = 0xf,
-        vaddr = 0xff,
-        paddr = 0xfff,
-        filesz = 0xffff,
-        memsz = 0xfffff,
-        align = 1,
     },
     {
         type = SegmentType.dynamic,
-- 
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