fix opening db through symlink or relative to root directory

Author: mlin

.github/workflows/tests.yml

@@ -25,7 +25,8 @@ jobs:
         /usr/local/bin/pip3 install pytest pytest-xdist
     - name: build
       run: |
-        CXXFLAGS=-I$(brew --prefix)/include LDFLAGS=-L$(brew --prefix)/lib \
+        CXXFLAGS="-I$(brew --prefix)/include -I$(brew --prefix)/opt/sqlite/include" \
+        LDFLAGS="-L$(brew --prefix)/lib -L$(brew --prefix)/opt/sqlite/lib" \
           cmake -DCMAKE_BUILD_TYPE=${{ matrix.BUILD_TYPE }} \
                 -DCMAKE_PREFIX_PATH=$(brew --prefix)/opt/sqlite \
                 -B build .

src/SQLiteNestedVFS.h

@@ -23,6 +23,7 @@
 #include <libgen.h>
 #include <memory>
 #include <string>
+#include <unistd.h>
 #include <vector>
 
 #include <iostream>
@@ -1116,8 +1117,17 @@ class VFS : public SQLiteVFS::Wrapper {
     // append a suffix as the inner db's filename (which won't actually exist on the host
     // filesystem, but xOpen() will recognize).
     int FullPathname(const char *zName, int nPathOut, char *zPathOut) override {
-        int rc = SQLiteVFS::Wrapper::FullPathname(zName, nPathOut, zPathOut);
-        if (rc != SQLITE_OK) {
+        std::string zName2(zName);
+        if (!zName2.empty() && zName2[0] != '/') {
+            if (getcwd(zPathOut, nPathOut) && !strcmp(zPathOut, "/")) {
+                // evading bug in sqlite3 os_unix.c unixFullPathname, when given a relative path
+                // and the cwd is / (this tends to happen in docker)
+                zName2 = "/" + zName2;
+            }
+        }
+        int rc = SQLiteVFS::Wrapper::FullPathname(zName2.c_str(), nPathOut, zPathOut);
+        if (rc != SQLITE_OK && rc != SQLITE_OK_SYMLINK) {
+            _DBG << "FullPathNameE " << rc << " " << sqlite3_errstr(rc) << _EOL;
             return rc;
         }
         std::string outer_db_filename(zPathOut);

test/test.py

@@ -130,6 +130,26 @@ def test_roundtrip_zstd(tmpdir, chinook_file):
     actual = [stmt.strip() for stmt in rslt.stdout.split(";\n")]
     assert actual == expected
 
+    # test reopen through symlink
+    linkpath = os.path.join(tmpdir, "symlink")
+    os.symlink(dbfn, linkpath)
+    assert os.path.realpath(linkpath) == os.path.realpath(dbfn)
+    linkcon = sqlite3.connect(f"file:{linkpath}?vfs=zstd", uri=True)
+    linkcon.execute("select 1")
+
+
+@pytest.mark.skipif(os.geteuid() != 0, reason="must run in docker")
+def test_db_in_root():
+    # regression test, create db with relative path to root directory
+    # (this tends to happen in docker)
+    con = sqlite3.connect(f":memory:")
+    con.enable_load_extension(True)
+    con.load_extension(os.path.join(BUILD, "zstd_vfs"))
+    os.chdir("/")
+    con = sqlite3.connect(f"file:test_in_root.db?vfs=zstd", uri=True)
+    con.executescript("CREATE TABLE hello(x INTEGER)")
+    con.commit()
+
 
 def test_vacuum(tmpdir, chinook_file):
     # open the zstd database