BSD support

README.md

@@ -61,9 +61,28 @@ This produces a single executable named `gg`.
   make MARCH=""
   ```
 
-  `gg` uses POSIX `memmem()` for matching; glibc (and other libcs) already
+  `gg` uses `memmem()` for matching; glibc (and other libcs) already
   accelerate that with SIMD on whatever CPU you run on. The default `-mavx2`
-  flag is therefore optional and can be dropped for maximum portability.
+  flag was removed from the Makefile because it is x86-only and unnecessary
+  (matching is done by the libc, not by hand-written SIMD), so the default
+  build is already maximally portable.
+
+- **Building on BSDs and macOS:**
+
+  `gg` builds and runs unchanged on FreeBSD, OpenBSD, NetBSD, DragonFly BSD,
+  and macOS/Darwin — just use the system compiler (`cc`/`clang`):
+
+  ```sh
+  make            # CC defaults to cc on systems without gcc
+  # or directly:
+  cc -O2 -std=c11 -Wall -Wextra     -D_POSIX_C_SOURCE=200809L -D_DEFAULT_SOURCE -o gg gg.c -lpthread
+  ```
+
+  To keep `gg` portable, the source no longer relies on any single libc's
+  conformance quirks: the `d_type` constants (`DT_DIR`, `DT_REG`, `DT_LNK`,
+  …) have portable fallbacks, `memmem()` is declared/provided where the libc
+  hides it, and the online-CPU count is obtained via `sysconf` on Linux or
+  `sysctlbyname("hw.ncpu")` on the BSDs and macOS.
 
 - **Cross-compiling for ARM / other targets:**
 
@@ -245,8 +264,10 @@ scaled better. `read()` also avoids faulting the entire file into memory.
 
 Yes. The only external links are `libc` and `libpthread`. There are no SIMD
 intrinsics in the source; matching uses `memmem()`, which your libc already
-accelerates with SIMD on the host CPU. It builds and runs on x86-64 and ARM64
-alike.
+accelerates with SIMD on the host CPU. It builds and runs unchanged on
+x86-64, ARM64, the BSD family (FreeBSD, OpenBSD, NetBSD, DragonFly) and
+macOS/Darwin — on any POSIX platform with a C11 compiler, `cc`/`gcc`/`clang`,
+and a `pthread` library.
 
 ### How fast is it?