Improve link mechanism and order

[waruqi]

Roadmap

• Support adjust and rewrite links order between add_deps, add_packages and add_links
• Support links group, -Wl,--start-group
• Support whole links, -Wl,--whole-archive
• Explicitly specify the linked file name

Related issues

• Library ordering with multiple dependencies #1240
• Link order problem with remote packages #566
• add_deps和add_links之间的连接顺序问题。 #1417
• add_links 不能重排链接顺序 #1293
• add_deps依赖顺序问题 #1144
• 问题：编译动态库时，如何方便地链接静态库和动态库 #1110
• add_links添加的多个库不能解决链接顺序问题 #1002
• add_packages 和 add_deps 之间无法控制链接顺序 #605
• 动态库B依赖由静态库链接出的动态库A，动态库B的链接命令中出现静态库 #1650
• 关于库的 group和whole 以及顺序问题 #4234
• 为 package 支持 link_group 功能 #4274

[waruqi]

Just a draft

Adjust the order of each configuration type

-- -la -ld -lb -lc -le -ls1 -ls2
add_syslinks("s1", "s2")
add_links("a")
add_links("b", "c", {order = 2})
add_links("d", {order = 1})
add_links("e")

-- -la -ld -lb -lc -le
add_ldflags("-la")
add_ldflags("-lb", "-lc", {order = 2})
add_ldflags("-ld", {order = 1})
add_ldflags("-le")

and add_includedirs, add_xxx etc, it supports all configurations

Adjust the link order between packages, deps, and options

-- -la -le -lf -lb -lc -ld -lg -ls1 -ls2
add_syslinks("s1", "s2")
add_links("a")
add_links("b", "c", {order = 4})
add_links("d", {order = 5})
add_links("package::e", {order = 1)
add_links("option::f", {order = 2)
add_links("dep::g")
add_packages("e")
add_options("f")
add_deps("g")

We can use namespaces such as package:: to individually adjust the link order of packages.

link group

--  -Wl,--start-group -la -lb -lc -Wl,--end-group -Wl,--start-group -lx -ly -lz -Wl,--end-group
add_links("a", "b", "c", {group = true})
add_syslinks("x", "y", "z", {group = true})

link group with deps, options and packages

--  -Wl,--start-group -la -lb -lc -ld -Wl,--end-group
add_links("a", "package::b", "dep::c", "option::d", {group = true}))
add_packages("b")
add_options("d")
add_deps("c")

link whole archive

--  -Wl,--whole-archive -la -lb -lc -Wl,--no-whole-archive
add_links("a", "b", "c", {whole = true})

link whole archive with deps, options and packages

--  -Wl,--whole-archive -la -lb -lc -ld -Wl,--no-whole-archive
add_links("a", "package::b", "dep::c", "option::d", {whole = true}))
add_packages("b")
add_options("d")
add_deps("c")

Explicitly specify the linked file name

libfoo.a libfoo.so in same directory

add_links("libfoo.a")
add_links("libfoo.so")
add_links("foo.lib")

[madhurajith]

Instead of repeating package, option, dependency using the "package::name" and setting the link order will it be better introduce "link_order" option for packages, options and dependencies?

Before,

add_links("package::e", {order = 1})
add_links("option::f", {order = 2})
add_links("dep::g")
add_packages("e")
add_options("f")
add_deps("g")

After,

add_packages("e", {link_order = 1})
add_options("f", {link_order = 2})
add_deps("g")

Instead of using a separate group flag, wouldn't it be better to use the "order" flag with two elements to denote the group? e.g.

add_syslinks("s1", "s2")
add_links("a")
add_links("b", "c", {order = 4})
add_links("d", {order = {5, 1}})
add_packages("e", {link_order = {1, 1}})
add_options("f", {link_order = {1, 2}})
add_deps("g", {link_order = 3, link_whole = true})
add_links("h", {order = {5, 2}})

This will end up with the command line,

-Wl,--start-group -le -lf -Wl,--end-group -Wl,--whole-archive -lg -Wl,--no-whole-archive -lb -lc -Wl,--start-group -ld -lh -Wl,--end-group -la -ls1 -ls2

[waruqi]

Instead of repeating package, option, dependency using the "package::name" and setting the link order will it be better introduce "link_order" option for packages, options and dependencies?

I still want to consider other configurations in package, such as add_includedirs("package::xxx") Maybe there will be ldflags, cflags in the future. .

Instead of using a separate group flag, wouldn't it be better to use the "order" flag with two elements to denote the group? e.g.

This is a bit too complicated, or we can use same order to put it in a group without using two elements.

add_links("a", "b", {order = 5})
add_links("c", {order = 5})

[xq114]

It's a bad idea using numbers to specify link orders. What matters is only the link order of some specific links and obviously a tree structure is more precise and robust.

[waruqi]

It's a bad idea using numbers to specify link orders. What matters is only the link order of some specific links and obviously a tree structure is more precise and robust.

The main reason is that the order of links between add_packages/add_options/add_links cannot be controlled. Are there any other better ideas?

[madhurajith]

@xq114 How to define the tree structure? should it be a single command like,

set_link_order("e", "f", {"a", "d", "c"}, {"deps::f", "options::b"}, "k")

[waruqi]

This does not conflict with tree inheritance, I only want to modify the link order between options/packages/links in the current target, and support link grouping.

target("test")
    -- need not `dep::xxx`, we only adjust the link order between options/packages/links in the current target
    add_linkorders("a", "b", "package::c", "option::d")
    add_linkorders("a", "b", "package::c", "option::d", {group = true})

how about this?

[waruqi]

about whole link

target("test")
    add_deps("a", {wholelink = true}) -- only for dep("xxx"), -lxxx
    add_links("a", "b", "c", {wholelink = true})
    add_options("a", "b", "c", {wholelink = true})
    add_packages("a", "b", "c", {wholelink = true})

[xq114]

@xq114 How to define the tree structure? should it be a single command like,

set_link_order("e", "f", {"a", "d", "c"}, {"deps::f", "options::b"}, "k")

You're right, I mean, we can use a couple of add_linkorders command to specify the link dependency tree. For example, the following code will generate a tree a->b->c->d c->e b->f

add_linkorders("a", "package::b", "c", "option::d")
add_linkorders("c", "package::e")
add_linkorders("b", "package::f)

If I want to modify the structure by adding g->a, just a modification to the first line would work, without rearranging the numbers denoting the position of linking.

Furthermore, it's better if a graph structure is supported, i.e. a->b->d a->c->d. The actual link order could be either a->b->c->d or a->c->b->d depending on implementation.

[madhurajith]

Does it respect package add_deps() by default?

package("foo")
    add_deps("bar")

Will the link order will be?

-lfoor -lbar

[waruqi]

Does it respect package add_deps() by default?

package("foo")
    add_deps("bar")

Will the link order will be?

-lfoor -lbar

right