Address @hobu 's review comment of https://github.com/OSGeo/PROJ/pull/1839#pullrequestreview-345535380

12 files changed, 90 insertions, 80 deletions

diff --git a/src/4D_api.cpp b/src/4D_api.cpp
index 71393dab..dabd44a0 100644
--- a/src/4D_api.cpp
+++ b/src/4D_api.cpp
@@ -1487,7 +1487,7 @@ PJ_INFO proj_info (void) {
         // Env var mostly for testing purposes and being independent from
         // an existing installation
         const char* ignoreUserWritableDirectory =
-            getenv("PROJ_IGNORE_USER_WRITABLE_DIRECTORY");
+            getenv("PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY");
         if( ignoreUserWritableDirectory == nullptr ||
             ignoreUserWritableDirectory[0] == '\0'  ) {
             buf = path_append(buf,
diff --git a/src/filemanager.cpp b/src/filemanager.cpp
index 0763181b..005e734b 100644
--- a/src/filemanager.cpp
+++ b/src/filemanager.cpp
@@ -1258,13 +1258,11 @@ static const char *proj_lib_name =
     nullptr;
 #endif
 
-static bool ignoreUserWritableDirectory() {
+static bool dontReadUserWritableDirectory() {
     // Env var mostly for testing purposes and being independent from
     // an existing installation
-    const char *envVarIgnoreUserWritableDirectory =
-        getenv("PROJ_IGNORE_USER_WRITABLE_DIRECTORY");
-    return envVarIgnoreUserWritableDirectory != nullptr &&
-           envVarIgnoreUserWritableDirectory[0] != '\0';
+    const char *envVar = getenv("PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY");
+    return envVar != nullptr && envVar[0] != '\0';
 }
 
 static void *
@@ -1336,7 +1334,7 @@ pj_open_lib_internal(projCtx ctx, const char *name, const char *mode,
             }
         }
 
-        else if (!ignoreUserWritableDirectory() &&
+        else if (!dontReadUserWritableDirectory() &&
                  (fid = open_file(
                       ctx, (pj_context_get_user_writable_directory(ctx, false) +
                             DIR_CHAR + name)
diff --git a/src/grids.cpp b/src/grids.cpp
index 24fcfe83..68bf8600 100644
--- a/src/grids.cpp
+++ b/src/grids.cpp
@@ -1837,17 +1837,20 @@ std::unique_ptr<NTv2GridSet> NTv2GridSet::open(PJ_CONTEXT *ctx,
         pj_ctx_set_errno(ctx, PJD_ERR_FAILED_TO_LOAD_GRID);
         return nullptr;
     }
-    if (memcmp(header + 56, "SECONDS", 7) != 0) {
+
+    constexpr int OFFSET_GS_TYPE = 56;
+    if (memcmp(header + OFFSET_GS_TYPE, "SECONDS", 7) != 0) {
         pj_log(ctx, PJ_LOG_ERROR, "Only GS_TYPE=SECONDS is supported");
         pj_ctx_set_errno(ctx, PJD_ERR_FAILED_TO_LOAD_GRID);
         return nullptr;
     }
 
     const bool must_swap = (header[8] == 11) ? !IS_LSB : IS_LSB;
+    constexpr int OFFSET_NUM_SUBFILES = 8 + 32;
     if (must_swap) {
         // swap_words( header+8, 4, 1 );
         // swap_words( header+8+16, 4, 1 );
-        swap_words(header + 8 + 32, 4, 1);
+        swap_words(header + OFFSET_NUM_SUBFILES, 4, 1);
         // swap_words( header+8+7*16, 8, 1 );
         // swap_words( header+8+8*16, 8, 1 );
         // swap_words( header+8+9*16, 8, 1 );
@@ -1858,7 +1861,7 @@ std::unique_ptr<NTv2GridSet> NTv2GridSet::open(PJ_CONTEXT *ctx,
     /*      Get the subfile count out ... all we really use for now.        */
     /* -------------------------------------------------------------------- */
     unsigned int num_subfiles;
-    memcpy(&num_subfiles, header + 8 + 32, 4);
+    memcpy(&num_subfiles, header + OFFSET_NUM_SUBFILES, 4);
 
     std::map<std::string, NTv2Grid *> mapGrids;
 
@@ -1878,25 +1881,31 @@ std::unique_ptr<NTv2GridSet> NTv2GridSet::open(PJ_CONTEXT *ctx,
         }
 
         // Byte swap interesting fields if needed.
+        constexpr int OFFSET_GS_COUNT = 8 + 16 * 10;
+        constexpr int OFFSET_SOUTH_LAT = 8 + 16 * 4;
         if (must_swap) {
-            swap_words(header + 8 + 16 * 4, sizeof(double), 6);
-            swap_words(header + 8 + 16 * 10, sizeof(int), 1);
+            // 6 double values: southLat, northLat, eastLon, westLon, resLat,
+            // resLon
+            swap_words(header + OFFSET_SOUTH_LAT, sizeof(double), 6);
+            swap_words(header + OFFSET_GS_COUNT, sizeof(int), 1);
         }
 
         std::string gridName;
         gridName.append(header + 8, 8);
 
         ExtentAndRes extent;
-        extent.westLon =
-            -to_double(header + 7 * 16 + 8) * DEG_TO_RAD / 3600.0; /* W_LONG */
-        extent.southLat =
-            to_double(header + 4 * 16 + 8) * DEG_TO_RAD / 3600.0; /* S_LAT */
-        extent.eastLon =
-            -to_double(header + 6 * 16 + 8) * DEG_TO_RAD / 3600.0; /* E_LONG */
-        extent.northLat =
-            to_double(header + 5 * 16 + 8) * DEG_TO_RAD / 3600.0; /* N_LAT */
-        extent.resLon = to_double(header + 9 * 16 + 8) * DEG_TO_RAD / 3600.0;
-        extent.resLat = to_double(header + 8 * 16 + 8) * DEG_TO_RAD / 3600.0;
+        extent.southLat = to_double(header + OFFSET_SOUTH_LAT) * DEG_TO_RAD /
+                          3600.0; /* S_LAT */
+        extent.northLat = to_double(header + OFFSET_SOUTH_LAT + 16) *
+                          DEG_TO_RAD / 3600.0; /* N_LAT */
+        extent.eastLon = -to_double(header + OFFSET_SOUTH_LAT + 16 * 2) *
+                         DEG_TO_RAD / 3600.0; /* E_LONG */
+        extent.westLon = -to_double(header + OFFSET_SOUTH_LAT + 16 * 3) *
+                         DEG_TO_RAD / 3600.0; /* W_LONG */
+        extent.resLat =
+            to_double(header + OFFSET_SOUTH_LAT + 16 * 4) * DEG_TO_RAD / 3600.0;
+        extent.resLon =
+            to_double(header + OFFSET_SOUTH_LAT + 16 * 5) * DEG_TO_RAD / 3600.0;
 
         if (!(fabs(extent.westLon) <= 4 * M_PI &&
               fabs(extent.eastLon) <= 4 * M_PI &&
@@ -1923,7 +1932,7 @@ std::unique_ptr<NTv2GridSet> NTv2GridSet::open(PJ_CONTEXT *ctx,
                extent.northLat * RAD_TO_DEG);
 
         unsigned int gs_count;
-        memcpy(&gs_count, header + 8 + 16 * 10, 4);
+        memcpy(&gs_count, header + OFFSET_GS_COUNT, 4);
         if (gs_count / columns != static_cast<unsigned>(rows)) {
             pj_log(ctx, PJ_LOG_ERROR,
                    "GS_COUNT(%u) does not match expected cells (%dx%d)",
@@ -2845,6 +2854,7 @@ ListOfHGrids pj_hgrid_init(PJ *P, const char *gridkey) {
 
 typedef struct { pj_int32 lam, phi; } ILP;
 
+// Apply bilinear interpolation for horizontal shift grids
 static PJ_LP pj_hgrid_interpolate(PJ_LP t, const HorizontalShiftGrid *grid,
                                   bool compensateNTConvention) {
     PJ_LP val, frct;
@@ -3283,6 +3293,8 @@ const GenericShiftGrid *pj_find_generic_grid(const ListOfGenericGrids &grids,
 
 // ---------------------------------------------------------------------------
 
+// Used by +proj=deformation and +proj=xyzgridshift to do bilinear interpolation
+// on 3 sample values per node.
 bool pj_bilinear_interpolation_three_samples(const GenericShiftGrid *grid,
                                              const PJ_LP &lp, int idx1,
                                              int idx2, int idx3, double &v1,
diff --git a/src/proj_internal.h b/src/proj_internal.h
index bb0e3453..a587c037 100644
--- a/src/proj_internal.h
+++ b/src/proj_internal.h
@@ -682,7 +682,7 @@ struct projGridChunkCache
 {
     bool enabled = true;
     std::string filename{};
-    long long max_size = 100 * 1024 * 1024;
+    long long max_size = 300 * 1024 * 1024;
     int ttl = 86400; // 1 day
 };
 
diff --git a/test/cli/Makefile.am b/test/cli/Makefile.am
index 42ee466d..417ec137 100644
--- a/test/cli/Makefile.am
+++ b/test/cli/Makefile.am
@@ -29,7 +29,7 @@ EXTRA_DIST = pj_out27.dist pj_out83.dist td_out.dist \
 		CMakeLists.txt
 
 testprojinfo-check:
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(TESTPROJINFO) $(PROJINFOEXE)
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(TESTPROJINFO) $(PROJINFOEXE)
 
 test27-check:
 	$(TEST27) $(PROJEXE)
@@ -41,24 +41,24 @@ testproj-check:
 	$(TESTPROJ) $(PROJEXE)
 
 testvarious-check:
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(TESTVARIOUS) $(CS2CSEXE)
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(TESTVARIOUS) $(CS2CSEXE)
 
 testdatumfile-check:
 	@if [ -f $(PROJ_LIB)/conus -a -f $(PROJ_LIB)/ntv1_can.dat -a -f $(PROJ_LIB)/MD -a -f $(PROJ_LIB)/ntf_r93.gsb -a -f $(PROJ_LIB)/egm96_15.gtx ]; then \
-	  PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(TESTDATUMFILE) $(CS2CSEXE) ; \
+	  PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(TESTDATUMFILE) $(CS2CSEXE) ; \
 	fi
 
 testign-check:
 	@if [ -f $(PROJ_LIB)/ntf_r93.gsb ] ; then \
-	  PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(TESTIGN) $(CS2CSEXE) ; \
+	  PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(TESTIGN) $(CS2CSEXE) ; \
 	fi
 
 testntv2-check:
 	@if [ -f $(PROJ_LIB)/ntv2_0.gsb -a -f $(PROJ_LIB)/conus -a -f $(PROJ_LIB)/ntv1_can.dat ] ; then \
-	  PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(TESTNTV2) $(CS2CSEXE) ; \
+	  PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(TESTNTV2) $(CS2CSEXE) ; \
 	fi
 
 testcct-check:
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(TESTCCT) $(CCTEXE)
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(TESTCCT) $(CCTEXE)
 
 check-local: testprojinfo-check test27-check test83-check testproj-check testvarious-check testdatumfile-check testign-check testntv2-check testcct-check
diff --git a/test/gie/Makefile.am b/test/gie/Makefile.am
index 783dfb7c..560fea0b 100644
--- a/test/gie/Makefile.am
+++ b/test/gie/Makefile.am
@@ -15,33 +15,33 @@ EXTRA_DIST = 4D-API_cs2cs-style.gie \
 PROJ_LIB ?= ../../data/for_tests
 
 4D-API-cs2cs-style: 4D-API_cs2cs-style.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 GDA: GDA.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 axisswap: axisswap.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 builtins: builtins.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 deformation: deformation.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 ellipsoid: ellipsoid.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 more_builtins: more_builtins.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 unitconvert: unitconvert.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 DHDN_ETRS89: DHDN_ETRS89.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 geotiff_grids: geotiff_grids.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 check-local: 4D-API-cs2cs-style GDA axisswap builtins deformation ellipsoid more_builtins unitconvert DHDN_ETRS89 geotiff_grids
diff --git a/test/gigs/Makefile.am b/test/gigs/Makefile.am
index 22ab099b..436a6e89 100644
--- a/test/gigs/Makefile.am
+++ b/test/gigs/Makefile.am
@@ -23,54 +23,54 @@ EXTRA_DIST = \
 PROJ_LIB ?= ../../data/for_tests
 
 5101.1: 5101.1-jhs.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5101.2: 5101.2-jhs.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5101.3: 5101.3-jhs.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5101.4: 5101.4-jhs-etmerc.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5102.1: 5102.1.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5103.1: 5103.1.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5103.2: 5103.2.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5103.3: 5103.3.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5105.2: 5105.2.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5106: 5106.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5107: 5107.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5109: 5109.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5111.1: 5111.1.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5112: 5112.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5113: 5113.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5201: 5201.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 5208: 5208.gie
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
 check-local: 5101.1 5101.2 5101.3 5101.4 5102.1 5103.1 5103.2 5103.3 5105.2 5106 5107 5109 5111.1 5112 5113 5201 5208
diff --git a/test/unit/CMakeLists.txt b/test/unit/CMakeLists.txt
index f5890f1a..845d07e5 100644
--- a/test/unit/CMakeLists.txt
+++ b/test/unit/CMakeLists.txt
@@ -71,7 +71,7 @@ target_link_libraries(proj_pj_transform_test
   ${PROJ_LIBRARIES})
 add_test(NAME proj_pj_transform_test COMMAND proj_pj_transform_test)
 set_property(TEST proj_pj_transform_test
-        PROPERTY ENVIRONMENT "PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
+        PROPERTY ENVIRONMENT "PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
 
 
 add_executable(proj_errno_string_test
@@ -82,7 +82,7 @@ target_link_libraries(proj_errno_string_test
   ${PROJ_LIBRARIES})
 add_test(NAME proj_errno_string_test COMMAND proj_errno_string_test)
 set_property(TEST proj_errno_string_test
-        PROPERTY ENVIRONMENT "PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
+        PROPERTY ENVIRONMENT "PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
 
 add_executable(proj_angular_io_test
   main.cpp
@@ -92,7 +92,7 @@ target_link_libraries(proj_angular_io_test
   ${PROJ_LIBRARIES})
 add_test(NAME proj_angular_io_test COMMAND proj_angular_io_test)
 set_property(TEST proj_angular_io_test
-        PROPERTY ENVIRONMENT "PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
+        PROPERTY ENVIRONMENT "PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
 
 add_executable(proj_context_test
   main.cpp
@@ -102,7 +102,7 @@ target_link_libraries(proj_context_test
   ${PROJ_LIBRARIES})
 add_test(NAME proj_context_test COMMAND proj_context_test)
 set_property(TEST proj_context_test
-        PROPERTY ENVIRONMENT "PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
+        PROPERTY ENVIRONMENT "PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
 
 if(MSVC AND BUILD_LIBPROJ_SHARED)
   # ph_phi2_test not compatible of a .dll build
@@ -115,7 +115,7 @@ else()
     ${PROJ_LIBRARIES})
   add_test(NAME pj_phi2_test COMMAND pj_phi2_test)
   set_property(TEST pj_phi2_test
-        PROPERTY ENVIRONMENT "PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
+        PROPERTY ENVIRONMENT "PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
 endif()
 
 add_executable(proj_test_cpp_api
@@ -136,7 +136,7 @@ target_link_libraries(proj_test_cpp_api
   ${SQLITE3_LIBRARY})
 add_test(NAME proj_test_cpp_api COMMAND proj_test_cpp_api)
 set_property(TEST proj_test_cpp_api
-        PROPERTY ENVIRONMENT "PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
+        PROPERTY ENVIRONMENT "PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
 
 
 add_executable(gie_self_tests
@@ -147,7 +147,7 @@ target_link_libraries(gie_self_tests
   ${PROJ_LIBRARIES})
 add_test(NAME gie_self_tests COMMAND gie_self_tests)
 set_property(TEST gie_self_tests
-        PROPERTY ENVIRONMENT "PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
+        PROPERTY ENVIRONMENT "PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests")
 
 
 add_executable(test_network
@@ -163,4 +163,4 @@ target_link_libraries(test_network
   ${SQLITE3_LIBRARY})
 add_test(NAME test_network COMMAND test_network)
 set_property(TEST test_network
-        PROPERTY ENVIRONMENT "PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests;PROJ_SOURCE_DATA=${PROJECT_SOURCE_DIR}/data")
+        PROPERTY ENVIRONMENT "PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data/for_tests;PROJ_SOURCE_DATA=${PROJECT_SOURCE_DIR}/data")
diff --git a/test/unit/Makefile.am b/test/unit/Makefile.am
index 86ed383a..11a6473c 100644
--- a/test/unit/Makefile.am
+++ b/test/unit/Makefile.am
@@ -23,7 +23,7 @@ pj_transform_test_SOURCES = pj_transform_test.cpp main.cpp
 pj_transform_test_LDADD = ../../src/libproj.la @GTEST_LIBS@
 
 pj_transform_test-check: pj_transform_test
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) ./pj_transform_test
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) ./pj_transform_test
 
 pj_phi2_test_SOURCES = pj_phi2_test.cpp main.cpp
 pj_phi2_test_LDADD = ../../src/libproj.la @GTEST_LIBS@
@@ -47,19 +47,19 @@ proj_context_test_SOURCES = proj_context_test.cpp main.cpp
 proj_context_test_LDADD = ../../src/libproj.la @GTEST_LIBS@
 
 proj_context_test-check: proj_context_test
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES ./proj_context_test
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES ./proj_context_test
 
 test_cpp_api_SOURCES = test_util.cpp test_common.cpp test_crs.cpp test_metadata.cpp test_io.cpp test_operation.cpp test_datum.cpp test_factory.cpp test_c_api.cpp test_grids.cpp main.cpp
 test_cpp_api_LDADD = ../../src/libproj.la @GTEST_LIBS@ @SQLITE3_LIBS@
 
 test_cpp_api-check: test_cpp_api
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) ./test_cpp_api
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) ./test_cpp_api
 
 gie_self_tests_SOURCES = gie_self_tests.cpp main.cpp
 gie_self_tests_LDADD = ../../src/libproj.la @GTEST_LIBS@ @SQLITE3_LIBS@
 
 gie_self_tests-check: gie_self_tests
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) ./gie_self_tests
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) ./gie_self_tests
 
 include_proj_h_from_c_SOURCES = include_proj_h_from_c.c
 
@@ -68,6 +68,6 @@ test_network_CXXFLAGS = @CURL_CFLAGS@ @CURL_ENABLED_FLAGS@
 test_network_LDADD = ../../src/libproj.la @GTEST_LIBS@ @SQLITE3_LIBS@ @CURL_LIBS@
 
 test_network-check: test_network
-	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) PROJ_SOURCE_DATA=$(PROJ_LIB) ./test_network
+	PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES PROJ_LIB=$(PROJ_LIB) PROJ_SOURCE_DATA=$(PROJ_LIB) ./test_network
 
 check-local: pj_transform_test-check pj_phi2_test-check proj_errno_string_test-check proj_angular_io_test-check proj_context_test-check test_cpp_api-check gie_self_tests-check test_network-check
diff --git a/test/unit/gie_self_tests.cpp b/test/unit/gie_self_tests.cpp
index fc0f0748..bcf31139 100644
--- a/test/unit/gie_self_tests.cpp
+++ b/test/unit/gie_self_tests.cpp
@@ -348,9 +348,9 @@ TEST(gie, info_functions) {
 
     /* proj_info()                                                            */
     /* this one is difficult to test, since the output changes with the setup */
-    putenv(const_cast<char *>("PROJ_IGNORE_USER_WRITABLE_DIRECTORY="));
+    putenv(const_cast<char *>("PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY="));
     info = proj_info();
-    putenv(const_cast<char *>("PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES"));
+    putenv(const_cast<char *>("PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES"));
 
     if (info.version[0] != '\0') {
         char tmpstr[64];
diff --git a/test/unit/proj_context_test.cpp b/test/unit/proj_context_test.cpp
index ec59590d..30d6d781 100644
--- a/test/unit/proj_context_test.cpp
+++ b/test/unit/proj_context_test.cpp
@@ -159,18 +159,18 @@ TEST(proj_context, read_grid_from_user_writable_directory) {
     auto filename = path + DIR_CHAR + "temp_proj_dic3";
     EXPECT_TRUE(createTmpFile(filename));
     {
-        // Check that with PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES (set by
+        // Check that with PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES (set by
         // calling script), we cannot find the file
         auto P = proj_create(ctx, "+init=temp_proj_dic3:MY_PIPELINE");
         EXPECT_EQ(P, nullptr);
         proj_destroy(P);
     }
     {
-        // Cancel the effect of PROJ_IGNORE_USER_WRITABLE_DIRECTORY
-        putenv(const_cast<char *>("PROJ_IGNORE_USER_WRITABLE_DIRECTORY="));
+        // Cancel the effect of PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY
+        putenv(const_cast<char *>("PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY="));
         auto P = proj_create(ctx, "+init=temp_proj_dic3:MY_PIPELINE");
         EXPECT_NE(P, nullptr);
-        putenv(const_cast<char *>("PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES"));
+        putenv(const_cast<char *>("PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES"));
         proj_destroy(P);
     }
     proj_context_destroy(ctx);
diff --git a/test/unit/test_network.cpp b/test/unit/test_network.cpp
index 688e61e5..241e6bbc 100644
--- a/test/unit/test_network.cpp
+++ b/test/unit/test_network.cpp
@@ -1577,7 +1577,7 @@ TEST(networking, download_whole_files) {
     unlink("proj_test_tmp/dvr90.tif");
     rmdir("proj_test_tmp");
 
-    putenv(const_cast<char *>("PROJ_IGNORE_USER_WRITABLE_DIRECTORY="));
+    putenv(const_cast<char *>("PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY="));
     putenv(const_cast<char *>("PROJ_USER_WRITABLE_DIRECTORY=./proj_test_tmp"));
     putenv(const_cast<char *>("PROJ_FULL_FILE_CHUNK_SIZE=100000"));
     auto ctx = proj_context_create();
@@ -1699,7 +1699,7 @@ TEST(networking, download_whole_files) {
     ASSERT_EQ(vectPct.back().second, 1.0);
 
     proj_context_destroy(ctx);
-    putenv(const_cast<char *>("PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES"));
+    putenv(const_cast<char *>("PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES"));
     putenv(const_cast<char *>("PROJ_USER_WRITABLE_DIRECTORY="));
     putenv(const_cast<char *>("PROJ_FULL_FILE_CHUNK_SIZE="));
     unlink("proj_test_tmp/cache.db");
@@ -1719,7 +1719,7 @@ TEST(networking, file_api) {
     unlink("proj_test_tmp/dvr90.tif");
     rmdir("proj_test_tmp");
 
-    putenv(const_cast<char *>("PROJ_IGNORE_USER_WRITABLE_DIRECTORY="));
+    putenv(const_cast<char *>("PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY="));
     putenv(const_cast<char *>("PROJ_USER_WRITABLE_DIRECTORY=./proj_test_tmp"));
     putenv(const_cast<char *>("PROJ_FULL_FILE_CHUNK_SIZE=30000"));
     auto ctx = proj_context_create();
@@ -1843,7 +1843,7 @@ TEST(networking, file_api) {
     ASSERT_TRUE(userData.in_seek);
 
     proj_context_destroy(ctx);
-    putenv(const_cast<char *>("PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES"));
+    putenv(const_cast<char *>("PROJ_SKIP_READ_USER_WRITABLE_DIRECTORY=YES"));
     putenv(const_cast<char *>("PROJ_USER_WRITABLE_DIRECTORY="));
     putenv(const_cast<char *>("PROJ_FULL_FILE_CHUNK_SIZE="));
     unlink("proj_test_tmp/cache.db");