zuo: fix some compiler warnings

Change parts of `zuo.c` to avoid warnings that show up with flags like

-Wall -Wextra -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -Wshadow -Wpointer-arith -Wcast-qual -pedantic -O2 -std=c11

Repair a bug in Windows for `fd-poll` that better testing exposed, but
also update test and docs to clarify that `fd-poll` is not so useful on
Windows.

racket/src/zuo/.github/scripts/msvcprep.bat

@@ -0,0 +1,42 @@
+
+REM  Find Visual Studio [Express] in one of the usual places.
+REM  Expects something like "x86", "amd64", or "x86_amd64" as an argument.
+
+set VCMODE=%1
+
+REM For 2022 and later, look in "Program Files"
+set Applications=%ProgramFiles%
+
+set VCVARBAT=%Applications%\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvarsall.bat
+
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvarsall.bat
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio\2022\Professional\VC\Auxiliary\Build\vcvarsall.bat
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio\2022\BuildTools\VC\Auxiliary\Build\vcvarsall.bat
+
+REM For 2019 and earlier, look in "Program Files (x86)"
+set Applications=%ProgramFiles(x86)%
+if "%Applications%" == "" set Applications=%ProgramFiles%
+
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio\2019\Enterprise\VC\Auxiliary\Build\vcvarsall.bat
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio\2019\Professional\VC\Auxiliary\Build\vcvarsall.bat
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvarsall.bat
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio\2019\BuildTools\VC\Auxiliary\Build\vcvarsall.bat
+
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio\2017\Enterprise\VC\Auxiliary\Build\vcvarsall.bat
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio\2017\Professional\VC\Auxiliary\Build\vcvarsall.bat
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvarsall.bat
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio\2017\BuildTools\VC\Auxiliary\Build\vcvarsall.bat
+
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio 14.0\vc\vcvarsall.bat
+
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio 13.0\vc\vcvarsall.bat
+
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio 12.0\vc\vcvarsall.bat
+
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio 11.0\vc\vcvarsall.bat
+
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio 10.0\vc\vcvarsall.bat
+
+if not exist "%VCVARBAT%" set VCVARBAT=%Applications%\Microsoft Visual Studio 9.0\vc\vcvarsall.bat
+
+"%VCVARBAT%" %VCMODE%

racket/src/zuo/.github/workflows/zuo-cflags.yml

@@ -0,0 +1,45 @@
+---
+name: Zuo with Strict Compiler Flags
+
+# yamllint disable-line rule:truthy
+on: [push, pull_request]
+
+jobs:
+  build-gcc:
+    runs-on: ubuntu-22.04
+
+    env:
+      CFLAGS: "-Werror -Wall -Wextra -Wstrict-prototypes -Wold-style-definition -Wshadow -Wpointer-arith -Wcast-qual -pedantic -O2 -std=c11 -D_POSIX_C_SOURCE=200809L"
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 100
+      - name: Compile
+        run: |
+          gcc -c $CFLAGS -DZUO_EMBEDDED zuo.c -o zuo_embed.o
+          gcc $CFLAGS zuo.c -o zuo
+      - name: Check
+        run: ./zuo build.zuo check
+
+  build-msvc:
+    runs-on: windows-2022
+
+    env:
+      CFLAGS: "/W1 /WX"
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 100
+      - name: Compile
+        shell: cmd
+        run: |
+          call .github\scripts\msvcprep.bat x86_amd64
+          cl /c %CFLAGS% /DZUO_EMBEDDED /Fo:zuo_embed.obj zuo.c
+          cl %CFLAGS% zuo.c -o zuo
+      - name: Check
+        shell: cmd
+        run: |
+          call .github\scripts\msvcprep.bat x86_amd64
+          zuo build.zuo check

racket/src/zuo/build.zuo

@@ -91,7 +91,7 @@
                           (lambda ()
                             (unless (= 0 (process-status
                                           (thread-process-wait
-                                           (hash-ref (process "to-run/zuo"
+                                           (hash-ref (process (.exe "to-run/zuo")
                                                               (at-source "tests/main.zuo"))
                                                      'process))))
                               (error "check failed")))))))

racket/src/zuo/tests/file-handle.zuo

@@ -155,9 +155,10 @@
                          'stdout 'pipe))])
   (define in (hash-ref ht 'stdout))
   (define out (hash-ref ht 'stdin))
-  (check (fd-poll (list in) 0) #f)
-  (check (fd-poll (list in out) 0) out)
-  (check (fd-poll (list in out)) out)
+  (unless (eq? 'windows (system-type)) ;; polling doesn't work on Windows pipes
+    (check (fd-poll (list in) 0) #f)
+    (check (fd-poll (list in out) 0) out)
+    (check (fd-poll (list in out)) out))
   (fd-write out "x")
   (check (fd-poll (list in)) in)
   (check (fd-poll (list in) 0) in)

racket/src/zuo/tests/path.zuo

@@ -102,7 +102,7 @@
        ".")
 (check (find-relative-path "home/zuo/src" "tmp/cache")
        (build-path ".." ".." ".." "tmp" "cache"))
-(check (find-relative-path "." "tmp/cache")
+(check (find-relative-path "." (build-path "tmp" "cache"))
        (build-path "tmp" "cache"))
 (check (find-relative-path "tmp/cache" ".")
        (build-path ".." ".."))
@@ -148,7 +148,7 @@
 (check-arg-fail (file-name-from-path 10) not-path)
 
 (check (path-replace-extension "a.c" ".o") "a.o")
-(check (path-replace-extension "p/a.c" ".o") (build-path "p" "a.o"))
-(check (path-replace-extension "p/.rc" ".o") (build-path "p" ".rc.o"))
+(check (path-replace-extension "p/a.c" ".o") (build-path "p/a.o"))
+(check (path-replace-extension "p/.rc" ".o") (build-path "p/.rc.o"))
 (check-arg-fail (path-replace-extension 10 "x") not-path)
 (check-arg-fail (path-replace-extension "x" 10) not-string)

racket/src/zuo/zuo-doc/lang-zuo.scrbl

@@ -1029,7 +1029,9 @@ until at least one is ready, and then it returns the first element of
 @racket[handles] that is ready. If @racket[timeout-msecs] is a number,
 then it specifies a number of milliseconds to wait; the result is
 @racket[#f] if no handle in @racket[handles] is ready before
-@racket[timeout-msecs] milliseconds pass.
+@racket[timeout-msecs] milliseconds pass. Polling typically does not
+work on Windows, because pipe handles claim to be ready for reading even
+when no data is available.
 
 @history[#:added "1.1"]}