Use the `png_jmpbuf' accessor, as recommended since libpng 1.4.0:
http://www.libpng.org/pub/png/src/libpng-1.2.x-to-1.4.x-summary.txt .

--- plotutils-2.6/libplot/z_write.c	2013-07-12 17:19:12.000000000 +0200
+++ plotutils-2.6/libplot/z_write.c	2013-07-12 17:19:07.000000000 +0200
@@ -164,7 +164,7 @@ _pl_z_maybe_output_image (S___(Plotter *
     }
 
   /* cleanup after libpng errors (error handler does a longjmp) */
-  if (setjmp (png_ptr->jmpbuf))
+  if (setjmp (png_jmpbuf (png_ptr)))
     {
       png_destroy_write_struct (&png_ptr, (png_info **)NULL);
       return -1;
@@ -444,7 +444,7 @@ _our_error_fn_stdio (png_struct *png_ptr
 #endif
     }
 
-  longjmp (png_ptr->jmpbuf, 1);
+  longjmp (png_jmpbuf (png_ptr), 1);
 }
 
 static void 
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<tr><td><span title='2021-10-10 16:22:40 +0300'>2021-10-10</span></td><td><a href='/guix/commit/gnu/packages/dbm.scm?id=b591052866e3956b543d130362d2f12fee0255e8'>gnu: bdb: Fix building on riscv64-linux.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/dbm.scm (bdb)[arguments]: Modify configure to build for
the currect architecture when building for riscv64-linux.
</span></span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2021-09-20 11:15:06 +0000'>2021-09-20</span></td><td><a href='/guix/commit/gnu/packages/dbm.scm?id=0d7888acf0791d1260ebf3f37ec50ad1dfcf359e'>gnu: bdb: Fix cross-compilation build errors.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/dbm.scm
  (bdb-4.8)[arguments]&lt;#:phases&gt;{update-config.sub}: Update 'config.sub'
  when cross-compiling for 'powerpc64le' or 'aarch64'.
</span></span></td><td>Maxime Devos</td></tr>
<tr><td><span title='2021-07-23 17:26:43 +0200'>2021-07-23</span></td><td><a href='/guix/commit/gnu/packages/dbm.scm?id=f94a0ce61ff89ad69c1ea327bb4ea763f0d5b2c0'>gnu: gdbm: Update to 1.20.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/dbm.scm (gdbm): Update to 1.20.
</span></span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2021-07-18 19:50:01 +0200'>2021-07-18</span></td><td><a href='/guix/commit/gnu/packages/dbm.scm?id=0e47fcced442d8e7c1b05184fdc1c14f10ed04ec'>Merge branch 'master' into core-updates</a></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-07-17 19:40:57 +0200'>2021-07-17</span></td><td><a href='/guix/commit/gnu/packages/dbm.scm?id=3918d6c4b6858dbc17ef1110ac2301d28238bb73'>gnu: gdbm: Use HTTPS home page.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/dbm.scm (gdbm)[home-page]: Use HTTPS.
</span></span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2021-03-24 20:50:44 +0200'>2021-03-24</span></td><td><a href='/guix/commit/gnu/packages/dbm.scm?id=2aab587f842908a886e3bd08b028885dddd650e0'>Merge remote-tracking branch 'origin/master' into core-updates</a></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2021-03-23 23:19:56 -0700'>2021-03-23</span></td><td><a href='/guix/commit/gnu/packages/dbm.scm?id=4cc2d2aa59910fcfd057bdee162bb96989b5a523'>gnu: bdb-4.8: Fix configure on powerpc64le-linux.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/dbm.scm (bdb-4.8)[arguments]: Modify 'configure phase to append
"--build=powerpc64le-unknown-linux-gnu" to configure's flags when compiling for
powerpc64le-linux.

Signed-off-by: Chris Marusich &lt;cmmarusich@gmail.com&gt;
</span></span></td><td>Leo Le Bouter</td></tr>