v2.2.0

mbt is the build tool for C and S/370 assembler projects that target MVS 3.8j: a project's Makefile is two lines, everything else is in project.toml, and compile, assemble, link and package all run on the host with the cc370 toolchain.

2.2.0 changes how a C module gets its startup. libc370 2.3.0 moved the C startup (@@CRT0) into libc.a, so mbt no longer links a startfile: the entry point decides, and the archive supplies it. It also makes the choice of @@START explicit instead of an accident of archive order. Requires cc370 >= 1.2.0; tested with cc370 1.4.0 and libc370 2.3.1.

Read this first

• startup = "crt0" / "crt1" can go. Both now mean "no explicit startfile"; mbt warns once per project while a module still names them. Drop the key together with a [toolchain] libc370 pin of at least 2.3.0: against an older libc370, a module without the key falls back to crt0.o.
• A dependency that defines @@START now needs a decision. libc370 is searched ahead of every dependency, so each module gets libc370's @@START unless it says dep_startup = true. If a dependency archive defines @@START and a module sets neither true nor false, make stops with exit 2 and names both. A CGI module that relies on its server's launcher sets dep_startup = true.
• An unknown startup value is an error (exit 2). It used to become crt0 silently.
• startup = false (own entry point) and startup = "crtm" are unchanged.
• A C module's startup no longer sits at offset 0 of the load module; the directory entry points at it. Anything that branches to a module's load point instead of its entry point would notice.

What changed

	before (2.1.x)	now (2.2.0)
C startup	crt0.o / crt1.o named on the link line	@@CRT0 taken from libc.a by the entry point
@@START	whichever archive came first; dependencies could win silently	libc370 first; a dependency's only with dep_startup = true
dependency defines @@START, module silent	built green with the wrong one	exit 2, naming module and archive
startup = "crt1"	the startfile without the thread driver	deprecated, one warning per project
unknown startup value	treated as crt0	configuration error
sysroot detection	by crt0.o	by libc.a, older sysroots still found
libc370 without @@CRT0 in libc.a	—	linked as before, with one warning

Install

mbt is consumed as a git submodule:

git -C mbt fetch --tags
git -C mbt checkout v2.2.0
git add mbt

Then remove startup = "crt0"/"crt1" from project.toml, pin [toolchain] libc370 = "2.3.1" (or at least 2.3.0), and add dep_startup where make asks for it. docs/MIGRATION.md describes the model in full.

Changelog

• The C startup comes out of libc.a; startup = becomes optional, the entry point decides (#158).
• libc370's @@START first for modules and tests; dep_startup selects a dependency's (#62).
• Sysroot found by libc.a; a cc370 floor of 1.2.0 when the CRT comes from the archive; one warning on an older libc370 (#160).
• docs/MIGRATION.md: ld370's default since cc370 1.2.0 and what each startup is for (#157); maintainer documentation moved to internals/ (#155, #156).