From 07aea4bf6a1d90e09396de4c02f96f545dd1989e Mon Sep 17 00:00:00 2001
From: Steven Hugg <hugg@fasterlight.com>
Date: Sat, 3 Oct 2026 15:51:12 +0200
Subject: [PATCH] cc65: only append warnings when errors are present

---
 CHANGELOG.md             |  1 +
 src/worker/tools/cc65.ts | 31 +++++++++++++++++++++----------
 test/cli/testworker.js   |  3 +++
 3 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2cf7fffd..af28bc88 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ See [extension/CHANGELOG.md](extension/CHANGELOG.md).
 - Emulators now run on a timeline: step back, seek, reverse run, `rbreak`, and deterministic replay with a replay-verification test that found determinism bugs in several platforms.
 - Step Over for C and assembly sources, a Breakpoints pane, and more breakpoint conditions.
 - Call Stack view renamed Call Graph, with clocks and more detail per line.
+- cc65/ca65/ld65 warnings are still ignored on a successful build, but are now listed with the errors when a build fails.
 - Reset clears the call graph; breakpoints are re-armed after a build.
 - Click the hex offset in the gutter to run to that line.
 - Waveform viewer for Verilog, with help and shortcuts.
diff --git a/src/worker/tools/cc65.ts b/src/worker/tools/cc65.ts
index 83eef8eb..265717fa 100644
--- a/src/worker/tools/cc65.ts
+++ b/src/worker/tools/cc65.ts
@@ -11,10 +11,19 @@ import { wasiFSAdapter, runWASITool, checkExitCode, readWASIOutput, readWASIOutp
 const CC65_SHARE = 'share/cc65';
 
 // cc65/ca65/ld65 report both errors and non-fatal warnings as
-// "<file>:<line>: <Warning|Error>: <msg>" on stderr; skip the warnings so a
-// clean build with only style/deprecation warnings doesn't fail.
+// "<file>:<line>: <Warning|Error>: <msg>" on stderr; warnings don't fail a
+// build, and are only reported when the build fails (see matchCC65Errors).
 const re_cc65_warning = /:\s*Warning:/;
 
+// collect errors from stderr; if the tool failed, append its warnings as context
+function matchCC65Errors(tool: string, errno: number, stderr: string[], errors: WorkerError[],
+    regex: RegExp, iline: number, imsg: number, path: string) {
+    const match = makeErrorMatcher(errors, regex, iline, imsg, path, 1);
+    stderr.filter(s => !re_cc65_warning.test(s)).forEach(match);
+    checkExitCode(tool, errno, stderr, errors);
+    if (errors.length) stderr.filter(s => re_cc65_warning.test(s)).forEach(match);
+}
+
 const wasiModules: { [tool: string]: WebAssembly.Module } = {};
 
 /**
@@ -155,8 +164,7 @@ export async function assembleCA65(step: BuildStep): Promise<BuildStepResult> {
             .concat(extraArgsFor('ca65', step.params.buildArgs));
         args.splice(args.length - 1, 0, ...extra);
         const { wasi, errno, stderr } = await runCC65Tool(step, 'ca65', args, (fs) => populateFiles(step, fs));
-        stderr.filter(s => !re_cc65_warning.test(s)).forEach(makeErrorMatcher(errors, /(.+?):(\d+): (.+)/, 2, 3, step.path, 1));
-        checkExitCode('ca65', errno, stderr, errors);
+        matchCC65Errors('ca65', errno, stderr, errors, /(.+?):(\d+): (.+)/, 2, 3, step.path);
         if (errors.length) {
             let listings : CodeListingMap = {};
             // TODO? change extension to .lst
@@ -199,14 +207,18 @@ export async function linkLD65(step: BuildStep): Promise<BuildStepResult> {
                 populateEntry(fs, params.cfgfile, store.getFileEntry(params.cfgfile), null);
             }
         });
-        // any non-warning ld65 message fails the build; again, "Warning:"-severity
+        // any non-warning ld65 message fails the build; "Warning:"-severity
         // output (e.g. the sp->c_sp deprecation from our prebuilt crt0.o/neslib2.lib)
-        // is non-fatal noise the user can't act on.
+        // is non-fatal noise, shown only if the link fails.
         for (let s of stderr) {
-            if (re_cc65_warning.test(s)) continue;
-            errors.push({ msg: s, line: 0 });
+            if (!re_cc65_warning.test(s)) errors.push({ msg: s, line: 0 });
         }
         checkExitCode('ld65', errno, stderr, errors);
+        if (errors.length) {
+            for (let s of stderr) {
+                if (re_cc65_warning.test(s)) errors.push({ msg: s, line: 0 });
+            }
+        }
         if (errors.length)
             return { errors: errors };
         var aout = readWASIOutput(wasi, "main");
@@ -349,8 +361,7 @@ export async function compileCC65(step: BuildStep): Promise<BuildStepResult> {
             });
             populateExtraFiles(step, fs, params.extra_compile_files);
         });
-        stderr.filter(s => !re_cc65_warning.test(s)).forEach(makeErrorMatcher(errors, /(.*?):(\d+): (.+)/, 2, 3, step.path, 1));
-        checkExitCode('cc65', errno, stderr, errors);
+        matchCC65Errors('cc65', errno, stderr, errors, /(.*?):(\d+): (.+)/, 2, 3, step.path);
         if (errors.length) return { errors };
         putWorkFile(destpath, readWASIOutputString(wasi, destpath));
     }
diff --git a/test/cli/testworker.js b/test/cli/testworker.js
index 313867ab..51375d9d 100644
--- a/test/cli/testworker.js
+++ b/test/cli/testworker.js
@@ -169,6 +169,9 @@ describe('Worker', function() {
   it('should NOT compile CC65 (compile error)', function(done) {
     compile('cc65', 'int main() {\nint x=1;\nprintf("%d",x);\nreturn x+2;\n}', 'nes', done, 0, 0, 1);
   });
+  it('should report CC65 warnings along with errors', function(done) {
+    compile('cc65', 'int main() {\nconst const int x=1;\nreturn y;\n}', 'nes', done, 0, 0, 2);
+  });
   it('should NOT compile CC65 (link error)', function(done) {
     compile('cc65', 'extern void bad();\nint main() {\nbad();\nreturn 0;\n}', 'nes', done, 0, 0, 1, {ignoreErrorPath:true});
   });