From f2ae6ba8091646583dcaebe2cd5146ce716ab528 Mon Sep 17 00:00:00 2001
From: Xi Ruoyao <xry111@xry111.site>
Date: Sat, 8 Oct 2022 19:02:47 +0800
Subject: [PATCH] rustc: demote curl and libssh2 to recommended

And, adjust LIBSSH2_SYS_USE_PKG_CONFIG according to if libssh2 is
installed.  Export it earlier so x.py build and x.py install will use
the same LIBSSH2_SYS_USE_PKG_CONFIG value.  This can reduce some
repeated building process.
---
 general/prog/rust.xml | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/general/prog/rust.xml b/general/prog/rust.xml
index d3cf0d3015..70428b9949 100644
--- a/general/prog/rust.xml
+++ b/general/prog/rust.xml
@@ -200,18 +200,25 @@
 
     <bridgehead renderas="sect4">Required</bridgehead>
     <para role="required">
-      <xref linkend="curl"/>,
-      <xref linkend="cmake"/>, and
-      <xref linkend="libssh2"/>
+      <xref linkend="cmake"/>
     </para>
 
     <bridgehead renderas="sect4">Recommended</bridgehead>
     <para role="recommended">
+      <xref linkend="curl"/>,
+      <xref linkend="libssh2"/>, and
       <xref linkend="llvm"/>
       (built with -DLLVM_LINK_LLVM_DYLIB=ON so that rust can link to
       system LLVM instead of building its shipped version)
     </para>
 
+    <note>
+      <para>
+        If a recommended dependency is not installed, a shipped copy in the
+        Rustc source tarball will be built and used.
+      </para>
+    </note>
+
     <bridgehead renderas="sect4">Optional</bridgehead>
     <para role="optional">
       <xref linkend="gdb"/> (used by the testsuite if it is present)
@@ -336,6 +343,8 @@ EOF</userinput></screen>
        src/tools/cargo/Cargo.toml &amp;&amp; -->
 
 <screen><userinput>export RUSTFLAGS="$RUSTFLAGS -C link-args=-lffi" &amp;&amp;
+{ [ ! -e /usr/include/libssh2.h ] ||
+  export LIBSSH2_SYS_USE_PKG_CONFIG=1; } &amp;&amp;
 python3 ./x.py build --exclude src/tools/miri</userinput></screen>
 
     <note>
@@ -414,8 +423,7 @@ python3 ./x.py build --exclude src/tools/miri</userinput></screen>
       Still as your normal user, do a DESTDIR install:
     </para>
 
-<screen><userinput>export LIBSSH2_SYS_USE_PKG_CONFIG=1 &amp;&amp;
-DESTDIR=${PWD}/install python3 ./x.py install &amp;&amp;
+<screen><userinput>DESTDIR=${PWD}/install python3 ./x.py install &amp;&amp;
 unset LIBSSH2_SYS_USE_PKG_CONFIG</userinput></screen>
 
     <para>
@@ -512,11 +520,10 @@ cp -a install/* /</userinput></screen>
       will not stop at the first error.
     </para>
 
+    <!-- https://github.com/alexcrichton/ssh2-rs/issues/173 -->
     <para>
-      <command>export LIBSSH2_SYS_USE_PKG_CONFIG=1</command>: On some systems,
-      cairo fails to link during the install because it cannot find libssh2.
-      This seems to fix it, but again the reason why the problem occurs is not
-      understood.
+      <command>export LIBSSH2_SYS_USE_PKG_CONFIG=1</command>: Allow
+      <command>cargo</command> to link to system libssh2.
     </para>
 
     <para>