term: move the term core to subprojects/term

The core now builds, tests, and benchmarks alone, as a Meson subproject
with no dependency on the main tree.

- include/term/ holds term.h and the header-only unicode/. src/ holds
  the core and its private headers. The main tree gets only
  include/term through term_dep, so it cannot reach a private header.
- The term tests, the term benchmarks, the Kitty parser suite, and
  tools/amalgamate.py and tools/generate_unicode.py move with it. The
  tests run as term:<name>.
- The main build passes its -march (arch_flag) and b_ndebug to the
  subproject. A directory configured before this commit needs
  meson configure -Dterm:arch_flag=-march=... once.
- The term tests compile with -UNDEBUG. They do work inside assert.
- The subproject exports term_test_dep with term_api.h, for the main
  tree's render, thumbnail, color, and selection tests.
- The Kitty bridge used struct vector2i and has not compiled since the
  public API redesign. It builds again. 2 of its 14 tests fail: REP
  after a tab, and a cursor report after a resize.
- dirgraph.py drops the term and unicode layers. Its self-test uses pty.
- The symbols test ignores the __odr_asan symbols that ASan adds.

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

1 files changed, 171 insertions, 0 deletions

diff --git a/src/compat.h b/src/compat.h
new file mode 100644
index 0000000..d1264fe
--- /dev/null
+++ b/src/compat.h
@@ -0,0 +1,171 @@
+#ifndef TERM_COMPAT_H
+#define TERM_COMPAT_H
+
+/*
+ * Compiler and libc differences, kept in one place. GCC and Clang use their
+ * builtins. MSVC uses its intrinsics. Any other compiler, and any build with
+ * TERM_NO_COMPILER_BUILTINS, uses plain C. Plain C gives the same results,
+ * only slower.
+ */
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#if defined(__GNUC__) || defined(__clang__)
+#define TERM_COMPILER_GNU 1
+#elif defined(_MSC_VER)
+#define TERM_COMPILER_MSVC 1
+#include <intrin.h>
+#endif
+
+#if !defined(TERM_NO_COMPILER_BUILTINS) && defined(TERM_COMPILER_GNU)
+#define TERM_HAVE_BUILTINS 1
+#elif !defined(TERM_NO_COMPILER_BUILTINS) && defined(TERM_COMPILER_MSVC)
+#define TERM_HAVE_MSVC_BITOPS 1
+#endif
+
+#if defined(TERM_COMPILER_GNU)
+#define TERM_HOT __attribute__((hot))
+#define TERM_NOINLINE __attribute__((noinline))
+#define TERM_ALWAYS_INLINE __attribute__((always_inline))
+#define TERM_MAYBE_UNUSED __attribute__((unused))
+#elif defined(TERM_COMPILER_MSVC)
+#define TERM_HOT
+#define TERM_NOINLINE __declspec(noinline)
+#define TERM_ALWAYS_INLINE __forceinline
+#define TERM_MAYBE_UNUSED
+#else
+#define TERM_HOT
+#define TERM_NOINLINE
+#define TERM_ALWAYS_INLINE
+#define TERM_MAYBE_UNUSED
+#endif
+
+#if defined(TERM_HAVE_BUILTINS)
+#define TERM_EXPECT(x, v) __builtin_expect((x), (v))
+#else
+#define TERM_EXPECT(x, v) (x)
+#endif
+
+/* term_ctz32(0) is 32 and term_ctz64(0) is 64 on every path. */
+#if defined(TERM_HAVE_BUILTINS)
+
+static inline int term_ctz32(uint32_t x) { return x ? __builtin_ctz(x) : 32; }
+static inline int term_popcount32(uint32_t x) { return __builtin_popcount(x); }
+static inline int term_ctz64(uint64_t x) { return x ? __builtin_ctzll(x) : 64; }
+static inline int term_popcount64(uint64_t x) { return __builtin_popcountll(x); }
+
+#else
+
+#if defined(TERM_HAVE_MSVC_BITOPS)
+static inline int term_ctz32(uint32_t x)
+{
+    unsigned long i;
+    return _BitScanForward(&i, x) ? (int)i : 32;
+}
+static inline int term_popcount32(uint32_t x) { return (int)__popcnt(x); }
+#else
+static inline int term_ctz32(uint32_t x)
+{
+    if (!x)
+        return 32;
+    int n = 0;
+    while (!(x & 1u)) {
+        x >>= 1;
+        n++;
+    }
+    return n;
+}
+static inline int term_popcount32(uint32_t x)
+{
+    int n = 0;
+    for (; x; x &= x - 1)
+        n++;
+    return n;
+}
+#endif
+
+/* Without builtins, the 64-bit forms are built from the 32-bit ones. */
+static inline int term_ctz64(uint64_t x)
+{
+    uint32_t lo = (uint32_t)x;
+    return lo ? term_ctz32(lo) : 32 + term_ctz32((uint32_t)(x >> 32));
+}
+
+static inline int term_popcount64(uint64_t x)
+{
+    return term_popcount32((uint32_t)x) + term_popcount32((uint32_t)(x >> 32));
+}
+
+#endif
+
+/* A spin-wait hint. Compilers without one get a no-op. */
+static inline void term_cpu_relax(void)
+{
+#if defined(TERM_COMPILER_GNU)
+#if defined(TERM_HAVE_BUILTINS) && defined(__x86_64__)
+    __builtin_ia32_pause();
+#elif defined(__aarch64__)
+    __asm__ __volatile__("yield");
+#endif
+#elif defined(TERM_COMPILER_MSVC)
+#if defined(_M_X64) || defined(_M_IX86)
+    _mm_pause();
+#elif defined(_M_ARM64)
+    __yield();
+#endif
+#endif
+}
+
+/* strdup is POSIX, so the core copies strings itself. */
+static inline char *term_strdup(const char *s)
+{
+    size_t n = strlen(s) + 1;
+    char *copy = malloc(n);
+    if (copy)
+        memcpy(copy, s, n);
+    return copy;
+}
+
+/* ASCII-only prefix test, as strncasecmp() does in the C locale. */
+static inline bool term_has_prefix_ci(const char *s, const char *prefix)
+{
+    for (; *prefix; prefix++, s++) {
+        unsigned char a = (unsigned char)*s;
+        unsigned char b = (unsigned char)*prefix;
+        if (a >= 'A' && a <= 'Z')
+            a += 'a' - 'A';
+        if (b >= 'A' && b <= 'Z')
+            b += 'a' - 'A';
+        if (a != b)
+            return false;
+    }
+    return true;
+}
+
+/* Allocates size bytes that start on an align-byte boundary. align must be a
+ * power of two. The raw pointer is stored just before the block, so
+ * term_aligned_free() can release it. C11 aligned_alloc() and POSIX
+ * posix_memalign() are not on every toolchain. */
+static inline void *term_aligned_alloc(size_t align, size_t size)
+{
+    if (size > SIZE_MAX - align - sizeof(void *))
+        return NULL;
+    void *raw = malloc(size + align + sizeof(void *));
+    if (!raw)
+        return NULL;
+    uintptr_t p = ((uintptr_t)raw + sizeof(void *) + align - 1) & ~((uintptr_t)align - 1);
+    ((void **)p)[-1] = raw;
+    return (void *)p;
+}
+
+static inline void term_aligned_free(void *p)
+{
+    if (p)
+        free(((void **)p)[-1]);
+}
+
+#endif