gnu: mandoc: Support zstd-compressed man pages.

Since #68242 Guix uses zstd compression for man pages.  Unfortunately,
upstream mandoc only supports gzip compressed man pages.  Luckily, zstd
provides a wrapper library which easily allows adapting software using
zlib to zstd compression.  This patch uses this wrapper library in
conjunction with mandoc to add support for zstd compression to it,
thereby allowing Guix man pages to be viewed with mandoc again.

Without this patch, mandoc is essentially defunct on Guix.

* gnu/packages/man.scm (mandoc): Support zstd compression.
* gnu/local.mk: Add new patch.
* gnu/packages/patches/mandoc-support-zstd-compression.patch: New file.

Signed-off-by: Maxim Cournoyer <[email protected]>
Change-Id: I49a6b9f81309aa1b9f0e5d19b1813dbac13cf968

3 files changed, 97 insertions, 18 deletions

diff --git a/gnu/local.mk b/gnu/local.mk
index e4a8220c83..328f6f2a27 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -1812,6 +1812,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/lxc-no-static-bin.patch	\
   %D%/packages/patches/mactelnet-remove-init.patch		\
   %D%/packages/patches/mailutils-variable-lookup.patch		\
+  %D%/packages/patches/mandoc-support-zstd-compression.patch	\
   %D%/packages/patches/make-impure-dirs.patch			\
   %D%/packages/patches/mariadb-rocksdb-atomic-linking.patch	\
   %D%/packages/patches/mathjax-disable-webpack.patch			\
diff --git a/gnu/packages/man.scm b/gnu/packages/man.scm
index 3148fcc8a1..1ff1fac991 100644
--- a/gnu/packages/man.scm
+++ b/gnu/packages/man.scm
@@ -37,6 +37,7 @@
   #:use-module (guix build-system gnu)
   #:use-module (guix build-system ruby)
   #:use-module (guix utils)
+  #:use-module (gnu packages)
   #:use-module (gnu packages base)
   #:use-module (gnu packages compression)
   #:use-module (gnu packages dbm)
@@ -273,30 +274,47 @@ pages into HTML format.")
               (method url-fetch)
               (uri (string-append "https://mandoc.bsd.lv/snapshots/mandoc-"
                                   version ".tar.gz"))
+              (patches (search-patches "mandoc-support-zstd-compression.patch"))
               (sha256
                (base32
                 "174x2x9ws47b14lm339j6rzm7mxy1j3qhh484khscw0yy1qdbw4b"))))
     (build-system gnu-build-system)
     (arguments
-     `(#:test-target "regress"
-       #:phases (modify-phases %standard-phases
-                  (add-before 'configure 'set-prefix
-                    (lambda* (#:key outputs #:allow-other-keys)
-                      (substitute* "configure"
-                        (("^CC=.*")
-                         (string-append "CC=" ,(cc-for-target) "\n"))
-                        (("^DEFCFLAGS=\\\\\"")
-                         "DEFCFLAGS=\"-O2 ")
-                        (("^UTF8_LOCALE=.*")      ;used for tests
-                         "UTF8_LOCALE=en_US.UTF-8\n")
-                        (("^MANPATH_(BASE|DEFAULT)=.*" _ which)
-                         (string-append "MANPATH_" which "="
-                                        "/run/current-system/profile/share/man\n"))
-                        (("^PREFIX=.*")
-                         (string-append "PREFIX=" (assoc-ref outputs "out")
-                                        "\n"))))))))
+      (list
+        #:test-target "regress"
+        #:make-flags
+        #~(list "VPATH=./zstd-src/zlibWrapper"
+                (string-join
+                  (list "CFLAGS=-DZWRAP_USE_ZSTD=1"
+                        "-I./zstd-src/zlibWrapper")
+                  " "))
+        #:phases
+        #~(modify-phases %standard-phases
+                         (add-after 'unpack 'unpack-zstd
+                           (lambda _
+                             (mkdir "zstd-src")
+                             (invoke "tar" "--strip-components=1" "-C"
+                                     "zstd-src" "-xf" #$(package-source zstd))))
+                         (add-before 'configure 'set-prefix
+                           (lambda* (#:key outputs #:allow-other-keys)
+                             (substitute*
+                               "configure"
+                               (("^CC=.*")
+                                (string-append "CC=" #$(cc-for-target) "\n"))
+                               (("^DEFCFLAGS=\\\\\"")
+                                "DEFCFLAGS=\"-O2 ")
+                               (("^UTF8_LOCALE=.*")      ;used for tests
+                                "UTF8_LOCALE=en_US.UTF-8\n")
+                               (("^MANPATH_(BASE|DEFAULT)=.*" _ which)
+                                (string-append
+                                  "MANPATH_" which "="
+                                  "/run/current-system/profile/share/man\n"))
+                               (("^PREFIX=.*")
+                                (string-append "PREFIX="
+                                               (assoc-ref outputs "out")
+                                               "\n"))))))))
     (native-inputs (list (libc-utf8-locales-for-target) perl)) ;used to run tests
-    (inputs (list zlib))
+    (inputs (list zlib (list zstd "lib")))
     (native-search-paths
      (list (search-path-specification
             (variable "MANPATH")
diff --git a/gnu/packages/patches/mandoc-support-zstd-compression.patch b/gnu/packages/patches/mandoc-support-zstd-compression.patch
new file mode 100644
index 0000000000..a73c762f3f
--- /dev/null
+++ b/gnu/packages/patches/mandoc-support-zstd-compression.patch
@@ -0,0 +1,60 @@
+mandoc upstream does not support zstd compression.  However, Guix uses zstd
+compression for its man pages, therefore — without support for this
+compression method — mandoc would be quite useless.  Hence, this patchset uses
+zlibWrapper from the zstd project to add zstd compression support to mandoc.
+
+Upstream-status: https://inbox.vuxu.org/mandoc-discuss/[email protected]/T/#t
+
+diff -upr mandoc-1.14.6.orig/Makefile mandoc-1.14.6/Makefile
+--- mandoc-1.14.6.orig/Makefile	2025-01-11 16:20:31.511129163 +0100
++++ mandoc-1.14.6/Makefile	2025-01-11 19:16:35.924788821 +0100
+@@ -251,7 +251,12 @@ LIBMANDOC_OBJS	 = $(LIBMAN_OBJS) \
+ 		   msec.o \
+ 		   preconv.o \
+ 		   read.o \
+-		   tag.o
++		   tag.o \
++		   zstd_zlibwrapper.o \
++		   gzclose.o \
++		   gzlib.o \
++		   gzread.o \
++		   gzwrite.o
+ 
+ ALL_COBJS	 = compat_err.o \
+ 		   compat_fts.o \
+Only in mandoc-1.14.6: Makefile.orig
+diff -upr mandoc-1.14.6.orig/configure mandoc-1.14.6/configure
+--- mandoc-1.14.6.orig/configure	2025-01-11 16:20:31.511129163 +0100
++++ mandoc-1.14.6/configure	2025-01-11 19:16:35.924788821 +0100
+@@ -430,7 +430,7 @@ fi
+ [ "${FATAL}" -eq 0 ] || exit 1
+ 
+ # --- LDADD ---
+-LDADD="${LDADD} ${LD_NANOSLEEP} ${LD_RECVMSG} ${LD_OHASH} -lz"
++LDADD="${LDADD} ${LD_NANOSLEEP} ${LD_RECVMSG} ${LD_OHASH} -lz -lzstd"
+ echo "selected LDADD=\"${LDADD}\"" 1>&2
+ echo "selected LDADD=\"${LDADD}\"" 1>&3
+ echo 1>&3
+Only in mandoc-1.14.6: configure.orig
+diff -upr mandoc-1.14.6.orig/read.c mandoc-1.14.6/read.c
+--- mandoc-1.14.6.orig/read.c	2025-01-11 16:35:03.825441715 +0100
++++ mandoc-1.14.6/read.c	2025-01-11 19:16:35.924788821 +0100
+@@ -37,7 +37,7 @@
+ #include <stdlib.h>
+ #include <string.h>
+ #include <unistd.h>
+-#include <zlib.h>
++#include <zstd_zlibwrapper.h>
+ 
+ #include "mandoc_aux.h"
+ #include "mandoc.h"
+@@ -627,7 +627,7 @@ mparse_open(struct mparse *curp, const char *file)
+ 	int		  fd, save_errno;
+ 
+ 	cp = strrchr(file, '.');
+-	curp->gzip = (cp != NULL && ! strcmp(cp + 1, "gz"));
++	curp->gzip = (cp != NULL && (! strcmp(cp + 1, "gz") || ! strcmp(cp + 1, "zst")));
+ 
+ 	/* First try to use the filename as it is. */
+ 
+Only in mandoc-1.14.6: read.c.orig