SDK: preserve user linker order after platform glue

docs/sdk-guide.md

@@ -178,6 +178,12 @@ When linking an executable (not compile-only), the SDK adds:
 - `sysroot/lib/crt1.o` — C runtime startup
 - `sysroot/lib/libc.a` — musl libc
 
+The injected glue and startup objects precede user linker inputs, and the final
+musl archive follows them. The SDK preserves user source, object, archive, and
+`-l` ordering between those boundaries. This also makes an explicit `-lc`, as
+emitted by some Autoconf projects, equivalent to the automatically linked libc
+without pulling musl's syscall definitions ahead of Kandelo's glue overrides.
+
 ### Sysroot platform libraries
 
 `scripts/build-musl.sh` also builds Kandelo's platform graphics shims into the

sdk/src/bin/cc.ts

@@ -24,6 +24,17 @@ export function buildClangArgs(userArgs: string[], toolchain: Toolchain, arch: W
   const parsed = parseArgs(filtered);
   const linking = needsLinking(parsed);
   const hasSourceFiles = parsed.sourceFiles.length > 0;
+  const forwardedArgs: string[] = [];
+  for (let i = 0; i < filtered.length; i++) {
+    const arg = filtered[i];
+    if (arg === '-shared' || arg === '-ldl') continue;
+    if (arg === '--kandelo-thread-slots' || arg === '--wasm-posix-thread-slots') {
+      i++;
+      continue;
+    }
+    if (arg.startsWith('--kandelo-thread-slots=') || arg.startsWith('--wasm-posix-thread-slots=')) continue;
+    forwardedArgs.push(arg);
+  }
 
   const args: string[] = [];
   const target = `--target=${targetTriple(arch)}`;
@@ -39,29 +50,14 @@ export function buildClangArgs(userArgs: string[], toolchain: Toolchain, arch: W
   }
   args.push(`--sysroot=${toolchain.sysroot}`);
 
-  if (parsed.compileOnly) args.push('-c');
-  if (parsed.preprocessOnly) args.push('-E');
-  if (parsed.assemblyOnly) args.push('-S');
-  if (parsed.outputFile) args.push('-o', parsed.outputFile);
-  args.push(...parsed.otherArgs);
-
-  args.push(...parsed.sourceFiles);
-  args.push(...parsed.objectFiles);
-  args.push(...parsed.archiveFiles);
-
-  // -fPIC is consumed by parseArgs (so the linker can see `parsed.pic`),
-  // but it must also reach clang at compile time so the resulting object
-  // uses PIC relocations. Without this a TU later linked into a shared
-  // library produces non-PIC objects and `wasm-ld --shared` rejects them
-  // with "R_WASM_MEMORY_ADDR_LEB cannot be used; recompile with -fPIC".
-  if (parsed.pic) args.push('-fPIC');
-
   if (linking) {
     if (parsed.shared) {
       // Shared library build: no CRT, no libc, no syscall glue
-      args.push(...SHARED_LINK_FLAGS);
+      args.push(...forwardedArgs, ...SHARED_LINK_FLAGS);
     } else {
-      // Executable build: link CRT, libc, and syscall glue
+      // Executable build: resolve user libraries after the platform glue that
+      // overrides musl symbols, then make the final libc archive available for
+      // everything still unresolved. Preserve the user's link-input order.
       const threadSlots = inferThreadSlotDeclaration(parsed, userArgs, {
         readFile: (path) => {
           try {
@@ -84,10 +80,13 @@ export function buildClangArgs(userArgs: string[], toolchain: Toolchain, arch: W
       }
       args.push(
         join(toolchain.sysroot, 'lib', 'crt1.o'),
+        ...forwardedArgs,
         join(toolchain.sysroot, 'lib', 'libc.a'),
         ...linkFlags(arch),
       );
     }
+  } else {
+    args.push(...forwardedArgs);
   }
 
   return args;

sdk/test/cc.test.ts

@@ -44,6 +44,33 @@ describe('buildClangArgs', () => {
     expect(args.join(' ')).toContain('channel_syscall.c');
   });
 
+  it('orders explicit libc and user libraries after syscall glue', () => {
+    const args = buildClangArgs([
+      'main.o',
+      '-L', '/deps/lib',
+      '-lxml2',
+      'support.a',
+      '-lc',
+      '-o', 'out.wasm',
+    ], toolchain);
+    const channelGlue = args.indexOf('/tmp/glue/channel_syscall.c');
+    const crt = args.indexOf('/tmp/sysroot/lib/crt1.o');
+    const main = args.indexOf('main.o');
+    const libraryPath = args.indexOf('-L');
+    const xml = args.indexOf('-lxml2');
+    const support = args.indexOf('support.a');
+    const explicitLibc = args.indexOf('-lc');
+    const finalLibc = args.indexOf('/tmp/sysroot/lib/libc.a');
+
+    expect(channelGlue).toBeLessThan(crt);
+    expect(crt).toBeLessThan(main);
+    expect(main).toBeLessThan(libraryPath);
+    expect(libraryPath).toBeLessThan(xml);
+    expect(xml).toBeLessThan(support);
+    expect(support).toBeLessThan(explicitLibc);
+    expect(explicitLibc).toBeLessThan(finalLibc);
+  });
+
   it('preprocess-only: no link flags', () => {
     const args = buildClangArgs(['-E', 'foo.c'], toolchain);
     expect(args).not.toContain('-Wl,--entry=_start');