This fixes

../../../../gcc-7.4.0/libstdc++-v3/libsupc++/new_opa.cc: In function ‘void* __gnu_cxx::aligned_alloc(std::size_t, std::size_t)’:
../../../../gcc-7.4.0/libstdc++-v3/libsupc++/new_opa.cc:78:10: error: ‘memalign’ was not declared in this scope
   return memalign (al, sz);
          ^~~~~~~~
../../../../gcc-7.4.0/libstdc++-v3/libsupc++/new_opa.cc:78:10: note: suggested alternative: ‘max_align_t’
   return memalign (al, sz);
          ^~~~~~~~
          max_align_t

diff --git a/libstdc++-v3/libsupc++/new_opa.cc b/libstdc++-v3/libsupc++/new_opa.cc
index 94e79cadb0e..084900e0daf 100644
--- a/libstdc++-v3/libsupc++/new_opa.cc
+++ b/libstdc++-v3/libsupc++/new_opa.cc
@@ -39,6 +39,8 @@ extern "C" void *memalign(std::size_t boundary, std::size_t size);
 # endif
 #endif
 
+#define memalign _aligned_malloc
+
 using std::new_handler;
 using std::bad_alloc;
 
bmit' value='switch'/></form></td></tr>
<tr><td class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
<table class='tabs'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=00262db23adb2666fa6d00d40e53f2145be26026'>refs</a><a class='active' href='/guix/log/gnu/packages/idutils.scm'>log</a><a href='/guix/tree/gnu/packages/idutils.scm?id=00262db23adb2666fa6d00d40e53f2145be26026'>tree</a><a href='/guix/commit/gnu/packages/idutils.scm?id=00262db23adb2666fa6d00d40e53f2145be26026'>commit</a><a href='/guix/diff/gnu/packages/idutils.scm?id=00262db23adb2666fa6d00d40e53f2145be26026'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/idutils.scm'>
<input type='hidden' name='id' value='00262db23adb2666fa6d00d40e53f2145be26026'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=00262db23adb2666fa6d00d40e53f2145be26026'>root</a>/<a href='/guix/log/gnu?id=00262db23adb2666fa6d00d40e53f2145be26026'>gnu</a>/<a href='/guix/log/gnu/packages?id=00262db23adb2666fa6d00d40e53f2145be26026'>packages</a>/<a href='/guix/log/gnu/packages/idutils.scm?id=00262db23adb2666fa6d00d40e53f2145be26026'>idutils.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/idutils.scm?id=00262db23adb2666fa6d00d40e53f2145be26026&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-11-10 20:18:37 +0200'>2018-11-10</span></td><td><a href='/guix/commit/gnu/packages/idutils.scm?id=1de2937283b3f19abf50af77f955a5dc4313755a'>gnu: idutils: Fix building with glibc@2.28.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2017-03-30 01:30:16 +0200'>2017-03-30</span></td><td><a href='/guix/commit/gnu/packages/idutils.scm?id=6fd52309b8f52c9bb59fccffac53e029ce94b698'>gnu: Use HTTPS for almost all gnu.org HOME-PAGEs.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>