Add build time option to make PROJ_LIB env var tested last (fixes #2399)

CMakeLists.txt

@@ -176,6 +176,13 @@ if(ENABLE_CURL)
   endif()
 endif()
 
+################################################################################
+
+option(PROJ_LIB_ENV_VAR_TRIED_LAST "Whether the PROJ_LIB environment variable should be tried after the hardcoded location" OFF)
+if(PROJ_LIB_ENV_VAR_TRIED_LAST)
+    add_definitions(-DPROJ_LIB_ENV_VAR_TRIED_LAST)
+endif()
+
 ################################################################################
 # threading configuration
 ################################################################################

configure.ac

@@ -321,6 +321,19 @@ AC_SUBST(CURL_LIBS,$CURL_LIBS)
 AC_SUBST(CURL_ENABLED_FLAGS,$CURL_ENABLED_FLAGS)
 AM_CONDITIONAL(HAVE_CURL, [test "x$FOUND_CURL" = "xyes"])
 
+
+dnl ---------------------------------------------------------------------------
+dnl proj-lib-env-var-tried-last
+dnl ---------------------------------------------------------------------------
+
+AC_ARG_ENABLE(proj-lib-env-var-tried-last,
+              AS_HELP_STRING([--enable-proj-lib-env-var-tried-last],
+                    [Whether the PROJ_LIB environment variable should be tried after the hardcoded location [default=no]]))
+
+if test "x$enable_proj_lib_env_var_tried_last" = "xyes"; then
+    AC_SUBST(PROJ_LIB_ENV_VAR_TRIED_LAST_FLAGS,-DPROJ_LIB_ENV_VAR_TRIED_LAST)
+fi
+
 dnl ---------------------------------------------------------------------------
 dnl Check for external Google Test
 dnl ---------------------------------------------------------------------------

docs/source/resource_files.rst

@@ -60,6 +60,11 @@ The following paths are checked in order:
   that since this is a hard-wired path setting, it only works if the whole
   PROJ installation is not moved somewhere else.
 
+  .. note:: if PROJ is built with the PROJ_LIB_ENV_VAR_TRIED_LAST CMake option /
+            --enable-proj-lib-env-var-tried-last configure switch, then this
+            hard-wired path will be tried before looking at the environment
+            variable :envvar:`PROJ_LIB`.
+
 - The current directory
 
 When networking capabilities are enabled, either by API with the

src/Makefile.am

@@ -6,7 +6,7 @@ TESTS = geodtest
 check_PROGRAMS = geodtest
 
 AM_CPPFLAGS =	-DPROJ_LIB=\"$(pkgdatadir)\" \
-		-DMUTEX_@MUTEX_SETTING@ -I$(top_srcdir)/include @SQLITE3_CFLAGS@ @TIFF_CFLAGS@ @TIFF_ENABLED_FLAGS@ @CURL_CFLAGS@ @CURL_ENABLED_FLAGS@
+		-DMUTEX_@MUTEX_SETTING@ -I$(top_srcdir)/include @SQLITE3_CFLAGS@ @TIFF_CFLAGS@ @TIFF_ENABLED_FLAGS@ @CURL_CFLAGS@ @CURL_ENABLED_FLAGS@ @PROJ_LIB_ENV_VAR_TRIED_LAST_FLAGS@
 AM_CXXFLAGS =    @CXX_WFLAGS@ @FLTO_FLAG@
 
 include_HEADERS = proj.h proj_experimental.h proj_constants.h geodesic.h \

src/filemanager.cpp

@@ -1362,6 +1362,12 @@ static const char *proj_lib_name =
     nullptr;
 #endif
 
+#ifdef PROJ_LIB_ENV_VAR_TRIED_LAST
+static bool gbPROJ_LIB_ENV_VAR_TRIED_LAST = true;
+#else
+static bool gbPROJ_LIB_ENV_VAR_TRIED_LAST = false;
+#endif
+
 static bool dontReadUserWritableDirectory() {
     // Env var mostly for testing purposes and being independent from
     // an existing installation
@@ -1448,8 +1454,10 @@ static void *pj_open_lib_internal(
             sysname = fname.c_str();
         }
 
-        /* if is environment PROJ_LIB defined */
-        else if (!(projLib = NS_PROJ::FileManager::getProjLibEnvVar(ctx))
+        /* if the environment PROJ_LIB defined, and *not* tried as last
+           possibility */
+        else if (!gbPROJ_LIB_ENV_VAR_TRIED_LAST &&
+                 !(projLib = NS_PROJ::FileManager::getProjLibEnvVar(ctx))
                       .empty()) {
             auto paths = NS_PROJ::internal::split(projLib, dirSeparator);
             for (const auto &path : paths) {
@@ -1461,17 +1469,42 @@ static void *pj_open_lib_internal(
                 if (fid)
                     break;
             }
+        }
+
+        else if ((sysname = get_path_from_relative_share_proj(
+                      ctx, name, fname)) != nullptr) {
             /* check if it lives in a ../share/proj dir of the proj dll */
-        } else if ((sysname = get_path_from_relative_share_proj(
-                        ctx, name, fname)) != nullptr) {
+        } else if (proj_lib_name != nullptr &&
+                   (fid = open_file(
+                        ctx,
+                        (std::string(proj_lib_name) + DIR_CHAR + name).c_str(),
+                        mode)) != nullptr) {
+
             /* or hardcoded path */
-        } else if ((sysname = proj_lib_name) != nullptr) {
-            fname = sysname;
+            fname = proj_lib_name;
             fname += DIR_CHAR;
             fname += name;
             sysname = fname.c_str();
+        }
+
+        /* if the environment PROJ_LIB defined, and tried as last possibility */
+        else if (gbPROJ_LIB_ENV_VAR_TRIED_LAST &&
+                 !(projLib = NS_PROJ::FileManager::getProjLibEnvVar(ctx))
+                      .empty()) {
+            auto paths = NS_PROJ::internal::split(projLib, dirSeparator);
+            for (const auto &path : paths) {
+                fname = path;
+                fname += DIR_CHAR;
+                fname += name;
+                sysname = fname.c_str();
+                fid = open_file(ctx, sysname, mode);
+                if (fid)
+                    break;
+            }
+        }
+
+        else {
             /* just try it bare bones */
-        } else {
             sysname = name;
         }
 
@@ -1516,21 +1549,35 @@ std::vector<std::string> pj_get_default_searchpaths(PJ_CONTEXT *ctx) {
         ignoreUserWritableDirectory[0] == '\0') {
         ret.push_back(proj_context_get_user_writable_directory(ctx, false));
     }
+
     const std::string envPROJ_LIB = NS_PROJ::FileManager::getProjLibEnvVar(ctx);
-    if (!envPROJ_LIB.empty()) {
-        ret.push_back(envPROJ_LIB);
-    }
-    if (envPROJ_LIB.empty()) {
-        const std::string relativeSharedProj = pj_get_relative_share_proj(ctx);
+    const std::string relativeSharedProj = pj_get_relative_share_proj(ctx);
+
+    if (gbPROJ_LIB_ENV_VAR_TRIED_LAST) {
+/* Situation where PROJ_LIB environment variable is tried in last */
+#ifdef PROJ_LIB
+        ret.push_back(PROJ_LIB);
+#endif
         if (!relativeSharedProj.empty()) {
             ret.push_back(relativeSharedProj);
         }
-    }
+        if (!envPROJ_LIB.empty()) {
+            ret.push_back(envPROJ_LIB);
+        }
+    } else {
+        /* Situation where PROJ_LIB environment variable is used if defined */
+        if (!envPROJ_LIB.empty()) {
+            ret.push_back(envPROJ_LIB);
+        } else {
+            if (!relativeSharedProj.empty()) {
+                ret.push_back(relativeSharedProj);
+            }
 #ifdef PROJ_LIB
-    if (envPROJ_LIB.empty()) {
-        ret.push_back(PROJ_LIB);
-    }
+            ret.push_back(PROJ_LIB);
 #endif
+        }
+    }
+
     return ret;
 }