Enable more build warnings for libc-bottom-half (WebAssembly#755)

While wasi-libc is compiled with `-Wall -Wextra` it ended up disabling a
lot of warnings as well to handle third-party code. This commit
reorganizes things by continuing to compile everything with `-Wall
-Wextra` but disabling lints is done exclusively for third-party code
rather than for all code in wasi-libc. In practice this means that
everything in `libc-bottom-half`, code written exclusively for this
repository, now has more lints firing. This additionally applies to
`test/src/*.c`. Much of this commit is handling these lints then and
adjusting a few patterns in places where necessary.

This commit additionally disables compiling with `-Werror` by default.
CI still enables this by default, but it means that new lints/warnings
won't be breaking for anyone else other than this repository's own CI
which should have pinned versions of Clang being used in various places.

Author: alexcrichton

.github/workflows/main.yml

@@ -47,7 +47,7 @@ jobs:
             os: ubuntu-22.04
             clang_version: 11
             upload: linux-x86_64-clang-11
-            args: -DSETJMP=OFF -DBUILD_SHARED=OFF
+            args: -DSETJMP=OFF -DBUILD_SHARED=OFF -DENABLE_WERROR=OFF
           - name: Build with LLVM 18
             os: ubuntu-24.04
             clang_version: 18
@@ -177,7 +177,7 @@ jobs:
 
     - name: Configure testing
       if: matrix.test
-      run: cmake -S . -B build -DBUILD_TESTS=ON -DENGINE=${{ env.ENGINE }}
+      run: cmake -S . -B build -DENABLE_WERROR=ON -DBUILD_TESTS=ON -DENGINE=${{ env.ENGINE }}
 
     - name: Build
       run: ninja -C build -v

CMakeLists.txt

@@ -50,6 +50,7 @@ option(SIMD "Whether or not to build simd-enabled intrinsics into wasi-libc" OFF
 option(BUILD_SHARED "Whether or not to build shared libraries" ON)
 option(CHECK_SYMBOLS "Whether or not to check the exported symbols of libc.a" OFF)
 set(WASI_SDK_VERSION "" CACHE STRING "Version information for wasi-sdk to embed in headers")
+option(ENABLE_WERROR "Whether to compile with `-Werror`" OFF)
 
 if(TARGET_TRIPLE MATCHES "-threads$")
   set(WASI p1)
@@ -195,25 +196,19 @@ add_compile_options(
   # TODO: Add -fno-signaling-nans when the compiler supports it.
   -fno-trapping-math
 
-  # Add all warnings, but disable a few which occur in third-party code.
-  -Wall -Wextra -Werror
-  -Wno-null-pointer-arithmetic
-  -Wno-unused-parameter
-  -Wno-sign-compare
-  -Wno-unused-variable
-  -Wno-unused-function
-  -Wno-ignored-attributes
-  -Wno-missing-braces
-  -Wno-ignored-pragmas
-  -Wno-unused-but-set-variable
-  -Wno-unknown-warning-option
-  -Wno-unterminated-string-initialization
+  # Add all warnings. Note that third-party code is compiled with extra flags
+  # to disable warnings that crop up.
+  -Wall -Wextra
 
   # Compiling assembly flags lots of arguments as unused but that's not too
   # interesting so just ignore that.
   $<$<COMPILE_LANGUAGE:ASM>:-Wno-unused-command-line-argument>
 )
 
+if (ENABLE_WERROR)
+  add_compile_options(-Werror)
+endif()
+
 # =============================================================================
 # Helper functions for adding libraries.
 

dlmalloc/CMakeLists.txt

@@ -1,3 +1,6 @@
+# Disable some warnings in this third-party code.
+add_compile_options(-Wno-null-pointer-arithmetic -Wno-unused-but-set-variable)
+
 add_object_library(dlmalloc src/dlmalloc.c)
 foreach(obj dlmalloc-shared dlmalloc-static)
   target_include_directories(${obj} PRIVATE include)

emmalloc/CMakeLists.txt

@@ -1,3 +1,5 @@
+# Disable some warnings in this third-party code.
+add_compile_options(-Wno-unused-function)
 add_object_library(emmalloc emmalloc.c)
 
 # emmalloc uses a lot of pointer type-punning, which is UB under strict

fts/CMakeLists.txt

@@ -1,3 +1,6 @@
+# Disable some warnings in this third-party code.
+add_compile_options(-Wno-unused-parameter -Wno-unused-variable)
+
 add_internal_object_library(fts musl-fts/fts.c)
 foreach(obj fts-shared fts-static)
   target_include_directories(${obj} PRIVATE . musl-fts)

libc-bottom-half/cloudlibc/src/common/errors.h

@@ -4,7 +4,7 @@
 #include <errno.h>
 #include <stdlib.h>
 
-static void translate_error(filesystem_error_code_t error) {
+static inline void translate_error(filesystem_error_code_t error) {
     switch (error) {
     case FILESYSTEM_ERROR_CODE_ACCESS:
         errno = EACCES;

libc-bottom-half/cloudlibc/src/libc/dirent/fdopendir.c

@@ -77,6 +77,7 @@ DIR *fdopendir(int fd) {
   dirp->dirent_size = 1;
   return dirp;
 #elif defined(__wasip3__)
+  (void) fd;
   // TODO(wasip3)
   errno = ENOTSUP;
   free(dirp);

libc-bottom-half/cloudlibc/src/libc/dirent/readdir.c

@@ -32,6 +32,7 @@ static_assert(DT_UNKNOWN == __WASI_FILETYPE_UNKNOWN, "Value mismatch");
 #endif
 
 // Grows a buffer to be large enough to hold a certain amount of data.
+#ifndef __wasip3__
 static struct dirent* grow(struct dirent **buffer, size_t *buffer_size, size_t target_size) {
   if (*buffer_size < target_size) {
     size_t new_size = *buffer_size;
@@ -47,6 +48,7 @@ static struct dirent* grow(struct dirent **buffer, size_t *buffer_size, size_t t
   }
   return *buffer;
 }
+#endif
 
 #if defined(__wasip1__)
 struct dirent *readdir(DIR *dirp) {

libc-bottom-half/cloudlibc/src/libc/dirent/scandirat.c

@@ -8,10 +8,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-static int sel_true(const struct dirent *de) {
-  return 1;
-}
-
 int __wasilibc_nocwd_scandirat(int dirfd, const char *dir, struct dirent ***res,
                                int (*sel)(const struct dirent *),
                                int (*cmp)(const struct dirent **, const struct dirent **)) {

libc-bottom-half/cloudlibc/src/libc/fcntl/openat.c

@@ -162,6 +162,9 @@ int __wasilibc_nocwd_openat_nomode(int fd, const char *path, int oflag) {
   // Update the descriptor table with the new handle
   return __wasilibc_add_file(new_handle, oflag);
 #elif defined(__wasip3__)
+  (void) fd;
+  (void) path;
+  (void) oflag;
   // TODO(wasip3)
   errno = ENOTSUP;
   return -1;