Fix infinite loop in file inferencing

re: Issue #2573

The file type inferencer in libdispatch/dinference.c has a simple
forward inference mechanism so that the occurrence of certain mode
values in a URL fragment implies inclusion of additional mode values.
This kind of inference is notorious for leading to cycles if not
careful. Unfortunately, this occurred in the one in dinference.c.

This was fixed by providing a more complicated, but more reliable inference
mechanism.

## Misc. Other Changes
* Found and fixed a couple of memory leaks.
* There is a recent problem in building HDF4 support on github actions. Fixed by using the internal HDF4 xdr capability.
* Some filter-related code was not being properly ifdef'd with ENABLE_NCZARRA_FILTERS.

.github/workflows/run_tests_osx.yml

@@ -7,7 +7,7 @@
 name: Run macOS-based netCDF Tests
 
 
-on: [pull_request, workflow_dispatch]
+on: [pull_request,workflow_dispatch]
 
 jobs:
 

.github/workflows/run_tests_ubuntu.yml

@@ -4,7 +4,7 @@
 
 name: Run Ubuntu/Linux netCDF Tests
 
-on: [pull_request, workflow_dispatch]
+on: [pull_request,workflow_dispatch]
 
 jobs:
 
@@ -42,7 +42,7 @@ jobs:
           wget https://support.hdfgroup.org/ftp/HDF/releases/HDF4.2.15/src/hdf-4.2.15.tar.bz2
           tar -jxf hdf-4.2.15.tar.bz2
           pushd hdf-4.2.15
-          ./configure --prefix=${HOME}/environments/${{ matrix.hdf5 }} --disable-static --enable-shared --disable-fortran --disable-netcdf --with-szlib
+          ./configure --prefix=${HOME}/environments/${{ matrix.hdf5 }} --disable-static --enable-shared --disable-fortran --disable-netcdf --with-szlib --enable-hdf4-xdr
           make -j
           make install -j
           popd
@@ -89,7 +89,7 @@ jobs:
           wget https://support.hdfgroup.org/ftp/HDF/releases/HDF4.2.15/src/hdf-4.2.15.tar.bz2
           tar -jxf hdf-4.2.15.tar.bz2
           pushd hdf-4.2.15
-          CC=mpicc ./configure --prefix=${HOME}/environments/${{ matrix.hdf5 }} --disable-static --enable-shared --disable-fortran --disable-netcdf --with-szlib --enable-parallel
+          CC=mpicc ./configure --prefix=${HOME}/environments/${{ matrix.hdf5 }} --disable-static --enable-shared --disable-fortran --disable-netcdf --with-szlib --enable-parallel --enable-hdf4-xdr
           make -j
           make install -j
           popd

.github/workflows/run_tests_win_cygwin.yml

@@ -1,6 +1,6 @@
 name: Run Cygwin-based tests
 
-on: [pull_request, workflow_dispatch]
+on: [pull_request,workflow_dispatch]
 
 env:
   SHELLOPTS: igncr

.github/workflows/run_tests_win_mingw.yml

@@ -9,7 +9,7 @@ name: Run MSYS2, MinGW64-based Tests
 env:
   CPPFLAGS: "-D_BSD_SOURCE"
 
-on: [pull_request, workflow_dispatch]
+on: [pull_request,workflow_dispatch]
 
 jobs:
 

libdispatch/dfile.c

@@ -1839,19 +1839,16 @@ NC_create(const char *path0, int cmode, size_t initialsz,
 
     TRACE(nc_create);
     if(path0 == NULL)
-        return NC_EINVAL;
+        {stat = NC_EINVAL; goto done;}
 
     /* Check mode flag for sanity. */
-    if ((stat = check_create_mode(cmode)))
-        return stat;
+    if ((stat = check_create_mode(cmode))) goto done;
 
     /* Initialize the library. The available dispatch tables
      * will depend on how netCDF was built
      * (with/without netCDF-4, DAP, CDMREMOTE). */
-    if(!NC_initialized)
-    {
-        if ((stat = nc_initialize()))
-            return stat;
+    if(!NC_initialized) {
+        if ((stat = nc_initialize())) goto done;
     }
 
     {
@@ -1863,10 +1860,7 @@ NC_create(const char *path0, int cmode, size_t initialsz,
 
     memset(&model,0,sizeof(model));
     newpath = NULL;
-    if((stat = NC_infermodel(path,&cmode,1,useparallel,NULL,&model,&newpath))) {
-	nullfree(newpath);
-        goto done;
-    }
+    if((stat = NC_infermodel(path,&cmode,1,useparallel,NULL,&model,&newpath))) goto done;
     if(newpath) {
         nullfree(path);
         path = newpath;
@@ -1918,7 +1912,7 @@ NC_create(const char *path0, int cmode, size_t initialsz,
         dispatcher = NC3_dispatch_table;
         break;
     default:
-        return NC_ENOTNC;
+        {stat = NC_ENOTNC; goto done;}
     }
 
     /* Create the NC* instance and insert its dispatcher and model */
@@ -1937,6 +1931,7 @@ NC_create(const char *path0, int cmode, size_t initialsz,
     }
 done:
     nullfree(path);
+    nullfree(newpath);
     return stat;
 }
 
@@ -1980,12 +1975,12 @@ NC_open(const char *path0, int omode, int basepe, size_t *chunksizehintp,
     TRACE(nc_open);
     if(!NC_initialized) {
         stat = nc_initialize();
-        if(stat) return stat;
+        if(stat) goto done;
     }
 
     /* Check inputs. */
     if (!path0)
-        return NC_EINVAL;
+        {stat = NC_EINVAL; goto done;}
 
     /* Capture the inmemory related flags */
     mmap = ((omode & NC_MMAP) == NC_MMAP);