fix(vfs): resolve make vfs build failures

[corylanou]

Summary

This PR fixes VFS build failures across all platforms (macOS and Linux) and adds CI protection to prevent future regressions.

The VFS builds were broken by commit f5b166a (feat(vfs): add observability PRAGMAs and relative time parsing #856) on Dec 1, 2025. The pre-built binaries in dist/ were from Nov 26 (before this change), which is why they still worked.

Root Cause Analysis

Issue 1: Missing -DSQLITE3VFS_LOADABLE_EXT C Preprocessor Flag

Symptom:

src/sqlite3vfs.h:7:10: fatal error: 'sqlite3-binding.h' file not found

Cause:
The sqlite3vfs.h header from the psanford/sqlite3vfs library uses conditional compilation:

#ifdef SQLITE3VFS_LOADABLE_EXT
#include "sqlite3ext.h"    // For loadable SQLite extensions
#else
#include "sqlite3-binding.h"  // For embedded SQLite (go-sqlite3 style)
#endif

The Go build step already passes -tags SQLITE3VFS_LOADABLE_EXT, but Go build tags only affect Go code compilation — they don't define C preprocessor macros. The subsequent gcc/clang commands that compile src/litestream-vfs.c into a shared library were missing the -DSQLITE3VFS_LOADABLE_EXT flag.

Without this flag, the C compiler tried to include sqlite3-binding.h (used by mattn/go-sqlite3 for embedded builds), which doesn't exist in our src/ directory. We bundle sqlite3ext.h instead because we're building a loadable extension.

Fix:
Added -DSQLITE3VFS_LOADABLE_EXT to all 5 VFS build targets in the Makefile:

• vfs (macOS native)
• vfs-linux-amd64
• vfs-linux-arm64
• vfs-darwin-amd64
• vfs-darwin-arm64

---

Issue 2: const char* vs char* Type Mismatch

Symptom:

src/litestream-vfs.c:14:14: error: conflicting types for 'GoLitestreamSetTime'
   14 | extern char* GoLitestreamSetTime(void* db, const char* timestamp);
      |              ^
cgo-gcc-export-header-prolog:58:14: note: previous declaration is here
   58 | extern char* GoLitestreamSetTime(void* dbPtr, char* timestamp);

Cause:
CGO generates C function declarations from Go //export comments. It does not preserve const qualifiers — all pointer parameters become non-const.

The C source file manually declared:

extern char* GoLitestreamSetTime(void* db, const char* timestamp);

But CGO generated (in litestream-vfs.h):

extern char* GoLitestreamSetTime(void* dbPtr, char* timestamp);

C treats const char* and char* as incompatible types, causing a compilation error.

Fix:

• Changed the declaration in src/litestream-vfs.c line 14 from const char* to char*
• Updated the call site at line 109 from (const char*)ts to (char*)ts

---

Issue 3: int64_t vs long long int Type Conflict (Linux Only)

Symptom (only after fixing Issues 1 & 2):

src/sqlite3.h:304:22: error: conflicting types for 'sqlite3_int64'
  304 | typedef sqlite_int64 sqlite3_int64;
      |                      ^~~~~~~~~~~~~
main.go:10:17: note: previous declaration of 'sqlite3_int64' with type 'long int'

Cause:
This is a subtle platform-specific issue with 64-bit integer types on Linux.

The Go CGO preamble had:

#include <stdint.h>
typedef int64_t sqlite3_int64;
typedef uint64_t sqlite3_uint64;

On Linux x86_64, <stdint.h> defines:

• int64_t as long int

But SQLite's sqlite3.h defines:

• sqlite3_int64 as long long int (via sqlite_int64)

Both long int and long long int are 64-bit on Linux x86_64, but C treats them as distinct, incompatible types. When we include both headers, the compiler sees two conflicting definitions for sqlite3_int64.

On macOS, both map to long long int, so this issue didn't appear there.

Fix:
Changed the CGO preamble in cmd/litestream-vfs/main.go to use SQLite's exact type definitions:

typedef long long int sqlite3_int64;
typedef unsigned long long int sqlite3_uint64;

This ensures type compatibility with sqlite3.h across all platforms.

---

Changes Summary

File	Change
Makefile	Added -DSQLITE3VFS_LOADABLE_EXT to gcc/clang in all 5 VFS targets
src/litestream-vfs.c	Changed const char* → char* in declaration (L14) and call (L109)
cmd/litestream-vfs/main.go	Changed int64_t/uint64_t → long long int/unsigned long long int
.github/workflows/commit.yml	Added VFS Build Test (macOS) and VFS Build Test (Linux) CI jobs

Test Plan

• make vfs builds successfully on macOS (native ARM64)
• make vfs-linux-amd64 builds successfully via Docker
• CI: VFS Build Test (macOS) passes
• CI: VFS Build Test (Linux) passes
• All other CI checks pass

Why CI Was Added

The VFS build jobs were recently added to release.yml but had never been triggered (no releases since they were added). This meant the build failures went unnoticed. Adding VFS build tests to commit.yml ensures every PR is tested before merge.

Fixes #873

🤖 Generated with Claude Code