Fixing Cross-Compiled SQLite3.exe Aborts on Windows via Cygwin

Issue Overview: Cross-Compiled SQLite3.exe Aborts Silently After Recent Code Changes

A user attempting to cross-compile sqlite3.exe for Windows using Cygwin and MinGW toolchains encountered a silent crash upon launching the generated executable. The Cygwin-native build worked as expected, but the Windows-targeted build (via x86_64-w64-mingw32-gcc or i686-w64-mingw32-gcc) exited immediately after displaying the version banner. This issue emerged after specific SQLite check-ins, notably those introducing UTF-16 console I/O improvements and the .www command. Key observations include:

1. No Error Messages: The Windows executable exited without diagnostic output, making root-cause analysis challenging.
2. Check-In Sensitivity: The problem surfaced between check-ins f0c5a86f (working) and f97f9944 (broken), though initial misidentification occurred due to stale build artifacts.
3. Cygwin vs. MinGW Behavior: The Cygwin-native sqlite3 worked, but cross-compiled versions failed, indicating platform-specific code interactions.
4. Tcl Integration Issues: Later builds exposed linker errors related to Tcl functions (e.g., Tcl_UnregisterChannel), complicating the troubleshooting process.
5. UTF-16 Console Handling: The silent abort was traced to Windows-specific UTF-16 console I/O logic conflicting with Cygwin/MinGW environments.

Possible Causes: Platform-Specific Code Paths and Build Configuration

1. Stale Build Artifacts

Partial rebuilds (without make clean or fossil clean) left outdated object files or scripts, leading to inconsistent behavior. The user initially suspected check-in 0b83e8f1 as the culprit, but this was a red herring caused by residual build files.

2. UTF-16 Console I/O Conflicts

Check-in f97f9944 introduced enhancements for UTF-16 console handling on Windows. However, cross-compilation via Cygwin/MinGW might have misapplied these changes, causing the CLI to abort when initializing the console.

3. Tcl Library Misconfiguration

The --enable-all flag activated Tcl integration, which failed during linking due to:

• Incorrect library paths (-L flags missing for Tcl stubs).
• Mismatched Tcl versions (Cygwin’s Tcl 8.6 vs. MinGW’s expectations).
• Build system changes in how Tcl is detected and linked (e.g., -ltclstub8.6).

4. Makefile Dependency Errors

Recent SQLite build system updates introduced dependency rules (e.g., src-verify) that broke Cygwin/MinGW cross-compilation workflows.

5. Cygwin/MinGW Toolchain Incompatibilities

Subtle differences in headers, libraries, or runtime behavior between Cygwin and Windows-targeted MinGW compilers caused silent crashes. Examples include:

• Missing WinMain entry point when linking Cygwin-specific libraries into Windows executables.
• Conflicts in low-level I/O or memory management APIs.

Troubleshooting Steps, Solutions & Fixes

1. Clean Build Environment

Problem: Stale artifacts masked the true breaking change.
Solution:

• Full Cleanup:

  fossil clean -x  # If using Fossil SCM
  # OR
  make distclean
  ./configure --enable-all --prefix=/usr
  make install
  

• Manual Cleanup: Delete all generated files (sqlite3.c, shell.c, opcodes.*, etc.) and rebuild from scratch.

2. Apply Platform-Specific Code Patches

Problem: UTF-16 console code activated erroneously in Cygwin/MinGW builds.
Solution: Modify platform guards in sqlite3_stdio.c and sqlite3_stdio.h to exclude Cygwin:

--- ext/misc/sqlite3_stdio.c
+++ ext/misc/sqlite3_stdio.c
@@ -11,7 +11,7 @@
 *************************************************************************
 **
 ** Implementation of standard I/O interfaces for UTF-8 that are missing
 ** on Windows.
 */
-#ifdef _WIN32
+#if defined(_WIN32) && !defined(__CYGWIN__)
 #ifndef _SQLITE3_STDIO_H_
 #include "sqlite3_stdio.h"
 #endif

Verification:

• Rebuild and test the cross-compiled sqlite3.exe.
• Confirm the CLI starts and accepts input without aborting.

3. Resolve Tcl Linking Errors

Problem: Undefined references to Tcl functions during shared library creation.
Solution A: Disable Tcl integration if unnecessary:

./configure --enable-all --disable-tcl --prefix=/usr

Solution B: Manually specify Tcl library paths:

gcc -shared tclsqlite3.c -o libsqlite3.dll -Wl,-ltclstub8.6 -L/usr/lib -L/usr/x86_64-w64-mingw32/sys-root/mingw/lib

Verification:

• Check for libtclstub8.6.a or libtclstub86.a in MinGW sysroot directories.
• Ensure TCL_STUB_LIB_SPEC is correctly defined in the build environment.

4. Fix Makefile Dependencies

Problem: Missing src-verify target blocking sqlite3.c generation.
Solution: Apply Makefile patch to correct dependencies:

--- Makefile.in
+++ Makefile.in
@@ -844,7 +844,7 @@
 	$(TCLSH_CMD) $(TOP)/tool/vdbe-compress.tcl <tsrc/vdbe.c >vdbe.new
 	mv vdbe.new tsrc/vdbe.c
 	cp fts5.c fts5.h tsrc
 	touch .target_source
 
-sqlite3.c:	.target_source $(TOP)/tool/mksqlite3c.tcl src-verify
+sqlite3.c:	.target_source $(TOP)/tool/mksqlite3c.tcl src-verify$(BEXE)

Verification:

• Rebuild sqlite3.c and confirm no "No rule to make target" errors.

5. Cross-Compilation Command Adjustments

Problem: Incorrect flags or missing static linking.
Solution: Use explicit MinGW compiler flags and static libgcc:

x86_64-w64-mingw32-gcc -DSQLITE_ENABLE_FTS5 -DFOR_WIN10 -static-libgcc shell.c sqlite3.c -o sqlite3.exe

Key Flags:

• -static-libgcc: Avoid dependency on MinGW runtime DLLs.
• -DFOR_WIN10: Ensure Windows 10+ API compatibility.

6. Test UTF-8/UTF-16 Handling

Problem: Silent abort due to console I/O failures.
Test Case: Execute a script with non-ASCII characters:

sqlite3.exe < multilang.txt

Contents of multilang.txt:

.mode box
CREATE TABLE בראשית(vn INT, lang TEXT, words TEXT);
INSERT INTO בראשית VALUES 
  (1, 'ar', 'في البدء خلق الله السموات والارض');
SELECT * FROM בראשית;

Expected Outcome:

• CLI displays non-ASCII text correctly.
• No crashes during table creation or output.

7. Address JimTCL Build Errors

Problem: jimsh0.c compilation failures on Windows.
Solution: Patch auto.def to prioritize _fullpath() over realpath():

--- auto.def
+++ auto.def
@@ -672,12 +672,12 @@
    # These headers are technically optional for JimTCL but necessary if
    # we want to use it for code generation:
    set sysh [cc-check-includes dirent.h sys/time.h]
-   if {$sysh && [cc-check-functions realpath]} {
-    define-append CFLAGS_JIMSH -DHAVE_REALPATH
-    define BTCLSH "\$(JIMSH)"
-   } elseif {$sysh && [cc-check-functions _fullpath]} {
+   if {$sysh && [cc-check-functions _fullpath]} {
     # _fullpath() is a Windows API
     define-append CFLAGS_JIMSH -DHAVE__FULLPATH
+    define BTCLSH "\$(JIMSH)"
+   } elseif {$sysh && [cc-check-functions realpath]} {
+    define-append CFLAGS_JIMSH -DHAVE_REALPATH
     define BTCLSH "\$(JIMSH)"
    } elseif {[file exists [get-define TCLSH_CMD]]} {
     set cgtcl [get-define TCLSH_CMD] 

Verification:

• Rebuild JimTCL (jimsh) and confirm code generation succeeds.

8. Final Build Workflow

Confirmed Working Command Sequence:

# Clean environment
fossil clean -x  # or git clean -fdx

# Configure and build
./configure --enable-all --prefix=/usr --disable-tcl
make install

# Cross-compile for Windows
i686-w64-mingw32-gcc -shared -DFOR_WIN10 -DSQLITE_ENABLE_FTS5 -static-libgcc sqlite3.c -o sqlite3.dll
x86_64-w64-mingw32-gcc -DSQLITE_ENABLE_FTS5 -DFOR_WIN10 -static-libgcc shell.c sqlite3.c -o sqlite3.exe

Post-Build Checks:

• Run sqlite3.exe on Windows and verify:
  • CLI prompt appears and remains responsive.
  • .help command lists all expected options, including .www.
  • Non-ASCII input/output functions correctly.

By systematically addressing build cleanliness, platform-specific code paths, Tcl integration, and MinGW toolchain configuration, users can resolve silent aborts in cross-compiled SQLite3 executables. The root cause—UTF-16 console I/O conflicts—highlights the importance of rigorous platform guards in cross-platform codebases.