Change Details

This implements https://sourceware.org/bugzilla/show_bug.cgi?id=26404 An `OVERWRITE_SECTIONS` command is a `SECTIONS` variant which contains several output section descriptions. The initial syntax is intentionally narrow to facilitate backward compatible extensions in the future. Symbol assignments cannot be used. OVERWRITE_SECTIONS does not specify a section order. Similar to `INSERT [BEFORE|AFTER]`, `LinkerScript::hasSectionsCommand` is not set, so the built-in rules (see `docs/ELF/linker_script.rst`) still apply. `OVERWRITE_SECTIONS` can be more convenient than `INSERT` because it does not need an anchor section. This feature is versatile. To list a few usage: * Use `section : { KEEP(...) }` to retain input sections under GC * Define encapsulation symbols (start/end) for an output section * Use `section : ALIGN(...) : { ... }` to overalign an output section (similar to ld64 `-sectalign`) When an output section is specified by both `OVERWRITE_SECTIONS` and `INSERT`, `INSERT` is processed after overwrite sections. To make this work, this patch changes `InsertCommand` to use name based matching instead of pointer based matching. This causes a difference when `INSERT` moves one output section more than once. This should not be used in practice (seems that in GNU ld the output sections may just disappear) A linker script can be used without -T/--script. This feature does not suppress orphan section placement so a wrong rule can make it easy to shoot oneself in the foot. The traditional `SECTIONS` commands are concatenated so a wrong rule can be more noticeable.

This implements https://sourceware.org/bugzilla/show_bug.cgi?id=26404 An `OVERWRITE_SECTIONS` command is a `SECTIONS` variant which contains several output section descriptions. The initial syntax is intentionally narrow to facilitate backward compatible extensions in the future. Symbol assignments cannot be used. OVERWRITE_SECTIONS does not specify a section order. Similar to `INSERT [BEFORE|AFTER]`, `LinkerScript::hasSectionsCommand` is not set, so the built-in rules (see `docs/ELF/linker_script.rst`) still apply. `OVERWRITE_SECTIONS` can be more convenient than `INSERT` because it does not need an anchor section. This feature is versatile. To list a few usage: * Use `section : { KEEP(...) }` to retain input sections under GC * Define encapsulation symbols (start/end) for an output section * Use `section : ALIGN(...) : { ... }` to overalign an output section (similar to ld64 `-sectalign`) When an output section is specified by both `OVERWRITE_SECTIONS` and `INSERT`, `INSERT` is processed after overwrite sections. To make this work, this patch changes `InsertCommand` to use name based matching instead of pointer based matching. This may cause a difference when `INSERT` moves one output section more than once. The duplicate commands should not be used in practice (seems that in GNU ld the output sections may just disappear). A linker script can be used without -T/--script. The traditional `SECTIONS` commands are concatenated and impose an order, so a wrong rule can be more noticeable. This feature if misused can be less noticeable, just like `INSERT`.

This implements https://sourceware.org/bugzilla/show_bug.cgi?id=26404 An `OVERWRITE_SECTIONS` command is a `SECTIONS` variant which contains several output section descriptions. The initial syntax is intentionally narrow to facilitate backward compatible extensions in the future. Symbol assignments cannot be used. OVERWRITE_SECTIONS does not specify a section order. Similar to `INSERT [BEFORE|AFTER]`, `LinkerScript::hasSectionsCommand` is not set, so the built-in rules (see `docs/ELF/linker_script.rst`) still apply. `OVERWRITE_SECTIONS` can be more convenient than `INSERT` because it does not need an anchor section. This feature is versatile. To list a few usage: * Use `section : { KEEP(...) }` to retain input sections under GC * Define encapsulation symbols (start/end) for an output section * Use `section : ALIGN(...) : { ... }` to overalign an output section (similar to ld64 `-sectalign`) When an output section is specified by both `OVERWRITE_SECTIONS` and `INSERT`, `INSERT` is processed after overwrite sections. To make this work, this patch changes `InsertCommand` to use name based matching instead of pointer based matching. This may causes a difference when `INSERT` moves one output section section more than once. ThisThe duplicate commands should not be used in practice (seems that in GNU ld the (seems that in GNU ld the output sections may just disappear). A linker script can be used without -T/--script. This feature does not suppressThe traditional `SECTIONS` orphan section placementcommands are concatenated and impose an order, so a wrong rule can make it easy to shoot oneself inbe more the foot. The traditional `SECTIONS` commands are concatenated so a wrong rule can be more noticeablenoticeable. This feature if misused can be less noticeable, just like `INSERT`.