Commit 813dac5 for zlib

commit 813dac5dcb5902ed241e9b0d38abd2d847a335a9
Author: Mark Adler <git@madler.net>
Date:   Wed Sep 16 17:55:36 2026 -0700

    Avoid use of EAGAIN or EWOULDBLOCK if not defined.

diff --git a/gzguts.h b/gzguts.h
index 266305d..55a69d9 100644
--- a/gzguts.h
+++ b/gzguts.h
@@ -103,6 +103,20 @@
 #  endif
 #endif

+#ifdef EAGAIN
+#  ifdef EWOULDBLOCK
+#    define BLOCKED(e) ((e) == EAGAIN || (e) == EWOULDBLOCK)
+#  else
+#    define BLOCKED(e) ((e) == EAGAIN)
+#  endif
+#else
+#  ifdef EWOULDBLOCK
+#    define BLOCKED(e) ((e) == EWOULDBLOCK)
+#  else
+#    define BLOCKED(e) (0)
+#  endif
+#endif
+
 /* unlike snprintf (which is required in C99), _snprintf does not guarantee
    null termination of the result -- however this is only used in gzlib.c where
    the result is assured to fit in the space provided */
diff --git a/gzread.c b/gzread.c
index 8b3e369..424f704 100644
--- a/gzread.c
+++ b/gzread.c
@@ -33,7 +33,7 @@ local int gz_load(gz_statep state, unsigned char *buf, unsigned len,
         *have += (unsigned)ret;
     } while (*have < len);
     if (ret < 0) {
-        if (errno == EAGAIN || errno == EWOULDBLOCK) {
+        if (BLOCKED(errno)) {
             state->again = 1;
             if (*have != 0)
                 return 0;
diff --git a/gzwrite.c b/gzwrite.c
index 44b6ae3..805c3f9 100644
--- a/gzwrite.c
+++ b/gzwrite.c
@@ -79,7 +79,7 @@ local int gz_comp(gz_statep state, int flush) {
             put = strm->avail_in > max ? max : strm->avail_in;
             writ = (int)write(state->fd, strm->next_in, put);
             if (writ < 0) {
-                if (errno == EAGAIN || errno == EWOULDBLOCK)
+                if (BLOCKED(errno))
                     state->again = 1;
                 gz_error(state, Z_ERRNO, zstrerror());
                 return -1;
@@ -114,7 +114,7 @@ local int gz_comp(gz_statep state, int flush) {
                       (unsigned)(strm->next_out - state->x.next);
                 writ = (int)write(state->fd, state->x.next, put);
                 if (writ < 0) {
-                    if (errno == EAGAIN || errno == EWOULDBLOCK)
+                    if (BLOCKED(errno))
                         state->again = 1;
                     gz_error(state, Z_ERRNO, zstrerror());
                     return -1;