support relative paths in QMAKE_RPATHDIR

... and make use of it in qt.prf.

[ChangeLog][qmake][Unix] Added support for relative paths in
QMAKE_RPATHDIR.

Note that this technically breaks backwards compatibility, as relative
paths were previously silently resolved against $$_PRO_FILE_PWD_. This
was not documented and seems rather useless, so i'm not worried.

Change-Id: I855042a8962ab34ad4617899a5b9825af0087f8a
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>
Reviewed-by: Jake Petroules <jake.petroules@theqtcompany.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

2 files changed, 39 insertions, 3 deletions

diff --git a/qmake/doc/src/qmake-manual.qdoc b/qmake/doc/src/qmake-manual.qdoc
index cfa288da82..535b500fd3 100644
--- a/qmake/doc/src/qmake-manual.qdoc
+++ b/qmake/doc/src/qmake-manual.qdoc
@@ -1845,6 +1845,22 @@
     The value of this variable is typically handled by
     qmake or \l{#QMAKESPEC}{qmake.conf} and rarely needs to be modified.
 
+    \section1 QMAKE_LFLAGS_REL_RPATH
+
+    Specifies the linker flags needed to enable relative paths in
+    \l{QMAKE_RPATHDIR}.
+
+    The value of this variable is typically handled by
+    qmake or \l{#QMAKESPEC}{qmake.conf} and rarely needs to be modified.
+
+    \section1 QMAKE_REL_RPATH_BASE
+
+    Specifies the string the dynamic linker understands to be the
+    location of the referring executable or library.
+
+    The value of this variable is typically handled by
+    qmake or \l{#QMAKESPEC}{qmake.conf} and rarely needs to be modified.
+
     \section1 QMAKE_LFLAGS_RPATHLINK
 
     Specifies the linker flags needed to use the values from
@@ -2095,6 +2111,13 @@
     executable at link time so that the paths will be preferentially
     searched at runtime.
 
+    When relative paths are specified, qmake will mangle them into a form
+    understood by the dynamic linker to be relative to the location of
+    the referring executable or library.
+    This is supported only by some platforms (currently Linux and
+    Darwin-based ones) and is detectable by checking whether
+    \l{QMAKE_REL_RPATH_BASE} is set.
+
     \section1 QMAKE_RPATHLINKDIR
 
     Specifies a list of library paths for the static linker to search for implicit
diff --git a/qmake/generators/unix/unixmake.cpp b/qmake/generators/unix/unixmake.cpp
index 1d9ebb35e3..57c0a97228 100644
--- a/qmake/generators/unix/unixmake.cpp
+++ b/qmake/generators/unix/unixmake.cpp
@@ -125,10 +125,23 @@ UnixMakefileGenerator::init()
         const ProStringList &rpathdirs = project->values("QMAKE_RPATHDIR");
         for (int i = 0; i < rpathdirs.size(); ++i) {
             QString rpathdir = rpathdirs[i].toQString();
-            if (rpathdir.length() > 1 && rpathdir.at(0) == '$' && rpathdir.at(1) != '(')
+            if (rpathdir.length() > 1 && rpathdir.at(0) == '$' && rpathdir.at(1) != '(') {
                 rpathdir.replace(0, 1, "\\$$");  // Escape from make and the shell
-            else if (!rpathdir.startsWith('@'))
-                rpathdir = QFileInfo(rpathdir).absoluteFilePath();
+            } else if (!rpathdir.startsWith('@') && fileInfo(rpathdir).isRelative()) {
+                QString rpathbase = project->first("QMAKE_REL_RPATH_BASE").toQString();
+                if (rpathbase.isEmpty()) {
+                    fprintf(stderr, "Error: This platform does not support relative paths in QMAKE_RPATHDIR (%s)\n",
+                                    rpathdir.toLatin1().constData());
+                    continue;
+                }
+                if (rpathbase.startsWith('$'))
+                    rpathbase.replace(0, 1, "\\$$");  // Escape from make and the shell
+                if (rpathdir == ".")
+                    rpathdir = rpathbase;
+                else
+                    rpathdir.prepend(rpathbase + '/');
+                project->values("QMAKE_LFLAGS").insertUnique(project->values("QMAKE_LFLAGS_REL_RPATH"));
+            }
             project->values("QMAKE_LFLAGS") += var("QMAKE_LFLAGS_RPATH") + escapeFilePath(rpathdir);
         }
     }