From 06e899b5e9a1334578870214f2ab6dc959354335 Mon Sep 17 00:00:00 2001
From: Mark Adler <madler@alumni.caltech.edu>
Date: Sat, 17 Dec 2016 13:20:47 -0800
Subject: [PATCH] Add run-time zlib version check to handle weak-linking case.

This allows for weak linking with a zlib library whose version is
older than the zlib header file used to compile pigz. The version
is checked at run time, and deflatePending() is not called if the
linked library does not have it. This commit adds a check as well
when invoked for the earliest acceptable version of zlib (1.2.3).
---
 pigz.c | 93 ++++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 65 insertions(+), 28 deletions(-)

diff --git a/pigz.c b/pigz.c
index 27fbd4d..1aa61d3 100644
--- a/pigz.c
+++ b/pigz.c
@@ -1237,6 +1237,29 @@ local unsigned long crc32z(unsigned long crc,
 /* compute check value depending on format */
 #define CHECK(a,b,c) (g.form == 1 ? adler32z(a,b,c) : crc32z(a,b,c))
 
+/* return the zlib version as an integer, where each component is interpreted
+   as a decimal number and converted to four hexadecimal digits -- e.g.
+   '1.2.11.1' -> 0x12b1, or return -1 if the string is not a valid version */
+local long zlib_vernum(void) {
+    char const *ver = zlibVersion();
+    long num = 0;
+    int left = 4;
+    int comp = 0;
+    do {
+        if (*ver >= '0' && *ver <= '9')
+            comp = 10 * comp + *ver - '0';
+        else {
+            num = (num << 4) + (comp > 0xf ? 0xf : comp);
+            left--;
+            if (*ver != '.')
+                break;
+            comp = 0;
+        }
+        ver++;
+    } while (left);
+    return left < 2 ? num << (left << 2) : -1;
+}
+
 #ifndef NOTHREAD
 /* -- threaded portions of pigz -- */
 
@@ -1756,23 +1779,28 @@ local void compress_thread(void *dummy)
                     strm.avail_in = (unsigned)len;
                     if (left || job->more) {
 #if ZLIB_VERNUM >= 0x1260
-                        deflate_engine(&strm, job->out, Z_BLOCK);
-
-                        /* add enough empty blocks to get to a byte boundary */
-                        (void)deflatePending(&strm, Z_NULL, &bits);
-                        if ((bits & 1) || !g.setdict)
-                            deflate_engine(&strm, job->out, Z_SYNC_FLUSH);
-                        else if (bits & 7) {
-                            do {        /* add static empty blocks */
-                                bits = deflatePrime(&strm, 10, 2);
-                                assert(bits == Z_OK);
-                                (void)deflatePending(&strm, Z_NULL, &bits);
-                            } while (bits & 7);
+                        if (zlib_vernum() >= 0x1260) {
                             deflate_engine(&strm, job->out, Z_BLOCK);
+
+                            /* add enough empty blocks to get to a byte
+                               boundary */
+                            (void)deflatePending(&strm, Z_NULL, &bits);
+                            if ((bits & 1) || !g.setdict)
+                                deflate_engine(&strm, job->out, Z_SYNC_FLUSH);
+                            else if (bits & 7) {
+                                do {        /* add static empty blocks */
+                                    bits = deflatePrime(&strm, 10, 2);
+                                    assert(bits == Z_OK);
+                                    (void)deflatePending(&strm, Z_NULL, &bits);
+                                } while (bits & 7);
+                                deflate_engine(&strm, job->out, Z_BLOCK);
+                            }
                         }
-#else
-                        deflate_engine(&strm, job->out, Z_SYNC_FLUSH);
+                        else
 #endif
+                        {
+                            deflate_engine(&strm, job->out, Z_SYNC_FLUSH);
+                        }
                         if (!g.setdict)     /* two markers when independent */
                             deflate_engine(&strm, job->out, Z_FULL_FLUSH);
                     }
@@ -2352,22 +2380,27 @@ local void single_compress(int reset)
             check = CHECK(check, strm->next_in, strm->avail_in);
             if (more || got) {
 #if ZLIB_VERNUM >= 0x1260
-                int bits;
-
-                DEFLATE_WRITE(Z_BLOCK);
-                (void)deflatePending(strm, Z_NULL, &bits);
-                if ((bits & 1) || !g.setdict)
-                    DEFLATE_WRITE(Z_SYNC_FLUSH);
-                else if (bits & 7) {
-                    do {
-                        bits = deflatePrime(strm, 10, 2);
-                        assert(bits == Z_OK);
-                        (void)deflatePending(strm, Z_NULL, &bits);
-                    } while (bits & 7);
-                    DEFLATE_WRITE(Z_NO_FLUSH);
+                if (zlib_vernum() >= 0x1260) {
+                    int bits;
+
+                    DEFLATE_WRITE(Z_BLOCK);
+                    (void)deflatePending(strm, Z_NULL, &bits);
+                    if ((bits & 1) || !g.setdict)
+                        DEFLATE_WRITE(Z_SYNC_FLUSH);
+                    else if (bits & 7) {
+                        do {
+                            bits = deflatePrime(strm, 10, 2);
+                            assert(bits == Z_OK);
+                            (void)deflatePending(strm, Z_NULL, &bits);
+                        } while (bits & 7);
+                        DEFLATE_WRITE(Z_NO_FLUSH);
+                    }
                 }
+                else
 #else
-                DEFLATE_WRITE(Z_SYNC_FLUSH);
+                {
+                    DEFLATE_WRITE(Z_SYNC_FLUSH);
+                }
 #endif
                 if (!g.setdict)             /* two markers when independent */
                     DEFLATE_WRITE(Z_FULL_FLUSH);
@@ -4304,6 +4337,10 @@ int main(int argc, char **argv)
         /* set all options to defaults */
         defaults();
 
+        /* check zlib version */
+        if (zlib_vernum() < 0x1230)
+           throw(EINVAL, "zlib version less than 1.2.3");
+
         /* process user environment variable defaults in GZIP */
         opts = getenv("GZIP");
         if (opts != NULL) {