Add ability to specify alternative sysroot for pkg-config files (GC issue #59)

Specifically, the new config.cc.pkgconfig.sysroot variable provides roughly
equivalent functionality to PKG_CONFIG_SYSROOT_DIR in pkg-config. For details
and limitations, see "Rewriting Installed Libraries System Root (sysroot)"
in the manual for details.

3 files changed, 114 insertions, 4 deletions

diff --git a/doc/manual.cli b/doc/manual.cli
index f24b429..66d0ffb 100644
--- a/doc/manual.cli
+++ b/doc/manual.cli
@@ -7585,6 +7585,11 @@ config.cc.libs
 
 config.cc.internal.scope
   cc.internal.scope
+
+config.cc.reprocess
+  cc.reprocess
+
+config.cc.pkgconfig.sysroot
 \
 
 Note that the compiler mode options are \"cross-hinted\" between \c{config.c}
@@ -7946,6 +7951,50 @@ prerequisite library, resolved using the above algorithm, and linked. In other
 words, in this case we end up with a binless library \c{lib{znonsense\}} that
 depends on \c{lib{z\}} instead of a single \c{lib{z\}} library.
 
+\h2#cc-import-installed-sysroot|Rewriting Installed Libraries System Root (sysroot)|
+
+Sometimes the installed libraries are moved to a different location after the
+installation. This is especially common in embedded development where the code
+is normally cross-compiled and the libraries for the target platform are
+placed into a host directory, called system root or \i{sysroot}, that doesn't
+match where these libraries were originally installed to. For example, the
+libraries might have been installed into \c{/usr/} but on the host machine
+they may reside in \c{/opt/target/usr/}. In this example, \c{/opt/target/} is
+the sysroot.
+
+While such relocations usually do not affect the library headers or binaries,
+they do break the \c{pkg-config}'s \c{.pc} files which often contain \c{-I}
+and \c{-L} options with absolute paths. Continue with the above example, a
+\c{.pc} file as originally installed may contain \c{-I/usr/include} and
+\c{-L/usr/lib} while now, that the libraries have been relocated to
+\c{/opt/target/}, they somehow need to be adjusted to
+\c{-I/opt/target/usr/include} and \c{-L/opt/target/usr/lib}.
+
+While it is possible (and perhaps correct) to accomplish this by fixing the
+\c{.pc} files to match the new location, it is not always possible or easy.
+As a result, \c{build2} provides a mechanism for automatically adjusting the
+system root in the \c{-I} and \c{-L} options extracted from \c{.pc} files.
+
+\N|This functionality is roughly equivalent to that provided with the
+\c{PKG_CONFIG_SYSROOT_DIR} environment variable by the \c{pkg-config}
+utility.|
+
+Specifically, the \c{config.cc.pkgconfig.sysroot} variable can be used to
+specify an alternative system root. When specified, all absolute paths in the
+\c{-I} and \c{-L} options that are not already in this directory will be
+rewritten to start with this sysroot.
+
+\N|Note that this mechanism is a workaround rather than a proper solution since
+it is limited to the \c{-I} and \c{-L} options. In particular, it does not
+handle any other options that may contain absolute paths nor \c{pkg-config}
+variables that may be queried.
+
+As a result, it should only be used for dealing with issues in third-party
+\c{.pc} files that do not handle relocation (for example, using the
+\c{${pcfiledir\}} built-in \c{pkg-config} variable). In particular, for
+\c{build2}-generated \c{.pc} files a \l{#install-reloc relocatable
+installation} should be used instead.|
+
 
 \h#cc-gcc|GCC Compiler Toolchain|
 
diff --git a/libbuild2/cc/init.cxx b/libbuild2/cc/init.cxx
index d766b30..1bddbb2 100644
--- a/libbuild2/cc/init.cxx
+++ b/libbuild2/cc/init.cxx
@@ -100,13 +100,19 @@ namespace build2
       vp.insert<strings> ("config.cc.loptions");
       vp.insert<strings> ("config.cc.aoptions");
       vp.insert<strings> ("config.cc.libs");
-      vp.insert<string>  ("config.cc.internal.scope");
+
+      vp.insert<string> ("config.cc.internal.scope");
+
+      vp.insert<bool> ("config.cc.reprocess"); // See cc.preprocess below.
+
+      vp.insert<abs_dir_path> ("config.cc.pkgconfig.sysroot");
 
       vp.insert<strings> ("cc.poptions");
       vp.insert<strings> ("cc.coptions");
       vp.insert<strings> ("cc.loptions");
       vp.insert<strings> ("cc.aoptions");
       vp.insert<strings> ("cc.libs");
+
       vp.insert<string>  ("cc.internal.scope");
       vp.insert<strings> ("cc.internal.libs");
 
@@ -177,7 +183,6 @@ namespace build2
 
       // Ability to disable using preprocessed output for compilation.
       //
-      vp.insert<bool> ("config.cc.reprocess");
       vp.insert<bool> ("cc.reprocess");
 
       // Register scope operation callback.
@@ -337,6 +342,15 @@ namespace build2
       if (lookup l = lookup_config (rs, "config.cc.reprocess"))
         rs.assign ("cc.reprocess") = *l;
 
+      // config.cc.pkgconfig.sysroot
+      //
+      // Let's look it up instead of just marking for saving to make sure the
+      // path is valid.
+      //
+      // Note: save omitted.
+      //
+      lookup_config (rs, "config.cc.pkgconfig.sysroot");
+
       // Load the bin.config module.
       //
       if (!cast_false<bool> (rs["bin.config.loaded"]))
diff --git a/libbuild2/cc/pkgconfig.cxx b/libbuild2/cc/pkgconfig.cxx
index b0b9675..ff84dc4 100644
--- a/libbuild2/cc/pkgconfig.cxx
+++ b/libbuild2/cc/pkgconfig.cxx
@@ -316,9 +316,15 @@ namespace build2
 
       assert (!ap.empty () || !sp.empty ());
 
-      // Append -I<dir> or -L<dir> option suppressing duplicates.
+      const scope& rs (*s.root_scope ());
+
+      const dir_path* sysroot (
+        cast_null<abs_dir_path> (rs["config.cc.pkgconfig.sysroot"]));
+
+      // Append -I<dir> or -L<dir> option suppressing duplicates. Also handle
+      // the sysroot rewrite.
       //
-      auto append_dir = [] (strings& ops, string&& o)
+      auto append_dir = [sysroot] (strings& ops, string&& o)
       {
         char c (o[1]);
 
@@ -337,6 +343,47 @@ namespace build2
         //    Note that we do normalize -L paths in the usrd logic later
         //    (but not when setting as *.export.loptions).
 
+        if (sysroot != nullptr)
+        {
+          // Notes:
+          //
+          // - The path might not be absolute (we only rewrite absolute ones).
+          //
+          // - Do this before duplicate suppression since options in ops
+          //   already have the sysroot rewritten.
+          //
+          // - Check if the path already starts with sysroot since some .pc
+          //   files might already be in a good shape (e.g., because they use
+          //   ${pcfiledir} to support relocation properly).
+          //
+          const char* op (o.c_str () + 2);
+          size_t on (o.size () - 2);
+
+          if (path_traits::absolute (op, on))
+          {
+            const string& s (sysroot->string ());
+
+            const char* sp (s.c_str ());
+            size_t sn (s.size ());
+
+            if (!path_traits::sub (op, on, sp, sn)) // Already in sysroot.
+            {
+              // Find the first directory seperator that seperates the root
+              // component from the rest of the path (think /usr/include,
+              // c:\install\include). We need to replace the root component
+              // with sysroot. If there is no separator (say, -Ic:) or the
+              // path after the separator is empty (say, -I/), then we replace
+              // the entire path.
+              //
+              size_t p (path_traits::find_separator (o, 2));
+              if (p == string::npos || p + 1 == o.size ())
+                p = o.size ();
+
+              o.replace (2, p - 2, s);
+            }
+          }
+        }
+
         for (const string& x: ops)
         {
           if (x.size () > 2 && x[0] == '-' && x[1] == c)