Add soversion, version macros, and reserved term_options words

The shared library now carries its major version in the SONAME
(libterm.so.0), so an ABI break gets a new file name. The header
gains TERM_VERSION, TERM_VERSION_MAJOR/MINOR/PATCH and
TERM_VERSION_CODE, and term_version() returns the code the library was
built with. A test checks the macros against meson.build's project
version and against the runtime value.

term_options ends with uint32_t reserved[8]. term_new() returns NULL if
a word is nonzero, so later versions can give those words a meaning
without misreading a caller's leftover data. All-zero options stay
valid.

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

3 files changed, 14 insertions, 0 deletions

diff --git a/src/meson.build b/src/meson.build
index 694ee0e..7223caa 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -1,5 +1,9 @@
 subdir('osc')
 
+# The SONAME carries the major version. An ABI break bumps it, so an old
+# binary keeps the old library.
+term_soversion = meson.project_version().split('.')[0]
+
 # The x86-64 SIMD kernels pick their level at run time (see simd.h), so the
 # library needs no ISA flags. -march in c_args sets the lowest level.
 term_lib = both_libraries('term',
@@ -23,6 +27,8 @@ term_lib = both_libraries('term',
   include_directories: term_private_inc,
   dependencies: [m_dep],
   gnu_symbol_visibility: 'hidden',
+  version: meson.project_version(),
+  soversion: term_soversion,
   install: true
 )
 
diff --git a/src/screen.c b/src/screen.c
index 87d6f2c..c41234f 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -847,6 +847,9 @@ struct term *term_new(const struct term_options *opt)
     static const struct term_options defaults;
     if (!opt)
         opt = &defaults;
+    for (size_t i = 0; i < sizeof(opt->reserved) / sizeof(opt->reserved[0]); i++)
+        if (opt->reserved[i])
+            return NULL;
     int cols = opt->size.x < 1 ? 80 : opt->size.x;
     int rows = opt->size.y < 1 ? 24 : opt->size.y;
     if (cols > TERM_MAX_COLS)
diff --git a/src/term.c b/src/term.c
index 1b16670..bf8f3cf 100644
--- a/src/term.c
+++ b/src/term.c
@@ -8,6 +8,11 @@ const char *term_unicode_version(void)
     return UNICODE_DATA_VERSION;
 }
 
+unsigned term_version(void)
+{
+    return TERM_VERSION_CODE;
+}
+
 void term_lock(struct term *t)
 {
     term_write_begin(t);