Emit C attributes via cbindgen

cbindgen.globdefs.toml

@@ -14,3 +14,11 @@
 
 # XXX: silences a warning
 "feature = no_std" = "__relibc__"
+
+# Ensure attributes are passed down from Rust
+# <features.h> must be included where attributes are used in relibc
+[fn]
+must_use = "__nodiscard"
+deprecated = "__deprecated"
+deprecated_with_note = "__deprecatedNote({})"
+no_return = "__noreturn"

include/features.h

@@ -3,26 +3,92 @@
  * Copyright (c) 2020 Rich Felker musl-libc
  */
 
-#ifndef _FEATURES_H
-#define _FEATURES_H
+#ifndef _FEATURES_H__RELIBC
+#define _FEATURES_H__RELIBC
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
+// Version metadata for feature gating
+// This is useful for divergent implementation specific behavior
+// glibc, ulibc, and likely others define a similar macro
+// musl does not define an equivalent macro
+#define __RELIBC__ 1
+#define __RELIBC__MAJOR 0
+#define __RELIBC__MINOR 2
+
+/*
+ * Sources:
+ * https://en.cppreference.com/w/c/language/attributes
+ * https://clang.llvm.org/docs/LanguageExtensions.html
+ * https://gcc.gnu.org/onlinedocs/cpp/_005f_005fhas_005fc_005fattribute.html
+ * https://gcc.gnu.org/onlinedocs/cpp/Standard-Predefined-Macros.html
+ */
+
+// Clang doesn't define __has_cpp_attribute if compiling C code
+#if !defined(__has_cpp_attribute)
+    #define __has_cpp_attribute(x) 0
 #endif
 
-#if __STDC_VERSION__ >= 199901L || defined(__cplusplus)
-#define __inline inline
-#elif !defined(__GNUC__)
-#define __inline
+// Clang doesn't define __has_c_attribute if compiling C++ code
+#if !defined(__has_c_attribute)
+    #define __has_c_attribute(x) 0
 #endif
 
-#if __STDC_VERSION__ >= 201112L
-#elif defined(__GNUC__)
-#define _Noreturn __attribute__((__noreturn__))
+// Check if C23+ attributes are available
+#if defined(__cplusplus)
+// HACK: GCC backports C++ attributes to C++98 but doesn't accept attributes
+// placed before the function like cbindgen emits.
+// Let's just disable attributes for C++98 by checking if a random C++11
+// feature is available.
+#define __HAS_ATTRIBUTE(x) __cpp_variable_templates &&__has_cpp_attribute(x)
 #else
-#define _Noreturn
+#define __HAS_ATTRIBUTE(x)                                                     \
+  (__has_c_attribute(x) || __STDC_VERSION__ >= 202311L ||                      \
+   __has_cpp_attribute(x))
+#endif
+
+// TODO: Not emitted with cbindgen
+#if __STDC_VERSION__ >= 199901L
+    #define __restrict restrict
+#elif !defined(__GNUC__)
+    #define __restrict
+#endif
+
+// TODO: Not emitted with cbindgen
+#if __STDC_VERSION__ >= 199901L || defined(__cplusplus)
+    #define __inline inline
+#elif !defined(__GNUC__)
+    #define __inline
+#endif
+
+// Analogous to Rust's Never type
+#if __HAS_ATTRIBUTE(noreturn)
+    #define __noreturn [[noreturn]]
+// #elif __STDC_VERSION__ >= 201112L
+// FIXME: cbindgen incorrectly places _Noreturn
+// #define __noreturn _Noreturn
+#elif defined(__GNUC__)
+    #define __noreturn __attribute__((__noreturn__))
+#else
+    #define __noreturn
+#endif
+
+// Analogous to Rust's #[must_use]
+// C23 only
+#if __HAS_ATTRIBUTE(nodiscard)
+    #define __nodiscard [[nodiscard]]
+    #define __nodiscardNote(x) [[nodiscard(x)]]
+#else
+    #define __nodiscard
+    #define __nodiscardNote(x)
+#endif
+
+// Analogous to Rust's #[deprecated]
+// C23 only
+#if __HAS_ATTRIBUTE(deprecated)
+    #define __deprecated [[deprecated]]
+    #define __deprecatedNote(x) [[deprecated(x)]]
+#else
+    #define __deprecated
+    #define __deprecatedNote(x)
 #endif
 
 #endif

src/header/assert/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = []
+sys_includes = ["features.h"]
 include_guard = "_RELIBC_ASSERT_H"
 trailer = "#include <bits/assert.h>"
 language = "C"
@@ -8,6 +8,3 @@ cpp_compat = true
 
 [enum]
 prefix_with_name = true
-
-[fn]
-no_return = "__attribute__((noreturn))"

src/header/ctype/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = ["bits/ctype.h"]
+sys_includes = ["bits/ctype.h", "features.h"]
 include_guard = "_RELIBC_CTYPE_H"
 language = "C"
 style = "Tag"

src/header/dirent/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = ["sys/types.h"]
+sys_includes = ["sys/types.h", "features.h"]
 include_guard = "_RELIBC_DIRENT_H"
 language = "C"
 style = "Both"

src/header/netdb/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = ["sys/socket.h", "netinet/in.h"]
+sys_includes = ["sys/socket.h", "netinet/in.h", "features.h"]
 include_guard = "_RELIBC_NETDB_H"
 trailer = "#include <bits/netdb.h>"
 language = "C"

src/header/pthread/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = ["sched.h", "time.h", "bits/pthread.h"]
+sys_includes = ["sched.h", "time.h", "bits/pthread.h", "features.h"]
 include_guard = "_RELIBC_PTHREAD_H"
 language = "C"
 style = "tag"

src/header/signal/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = ["bits/signal.h", "stdint.h", "sys/types.h", "time.h", "bits/pthread.h"]
+sys_includes = ["bits/signal.h", "stdint.h", "sys/types.h", "time.h", "bits/pthread.h", "features.h"]
 include_guard = "_RELIBC_SIGNAL_H"
 trailer = "#include <bits/signal.h>"
 language = "C"

src/header/stdio/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = ["stdarg.h", "stddef.h", "stdint.h", "sys/types.h"]
+sys_includes = ["stdarg.h", "stddef.h", "stdint.h", "sys/types.h", "features.h"]
 include_guard = "_RELIBC_STDIO_H"
 trailer = "#include <bits/stdio.h>"
 language = "C"

src/header/stdlib/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = ["stddef.h", "alloca.h", "wchar.h"]
+sys_includes = ["stddef.h", "alloca.h", "wchar.h", "features.h"]
 include_guard = "_RELIBC_STDLIB_H"
 trailer = "#include <bits/stdlib.h>"
 language = "C"
@@ -8,6 +8,3 @@ cpp_compat = true
 
 [enum]
 prefix_with_name = true
-
-[fn]
-no_return = "__attribute__((noreturn))"

src/header/sys_time/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = ["sys/types.h"]
+sys_includes = ["sys/types.h", "features.h"]
 include_guard = "_SYS_TIME_H"
 language = "C"
 trailer = "#include <bits/sys/time.h>"

src/header/sys_types/cbindgen.toml

@@ -7,6 +7,7 @@ sys_includes = [
     "stddef.h",
     "sys/select.h",
     "bits/pthread.h",
+    "features.h",
 ]
 
 include_guard = "_SYS_TYPES_H"

src/header/termios/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = ["stdint.h"]
+sys_includes = ["stdint.h", "features.h"]
 include_guard = "_RELIBC_TERMIOS_H"
 language = "C"
 style = "Tag"

src/header/time/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = ["sys/types.h", "stdint.h", "stddef.h"]
+sys_includes = ["sys/types.h", "stdint.h", "stddef.h", "features.h"]
 include_guard = "_RELIBC_TIME_H"
 language = "C"
 style = "Tag"

src/header/unistd/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = ["stddef.h", "stdint.h", "sys/types.h"]
+sys_includes = ["stddef.h", "stdint.h", "sys/types.h", "features.h"]
 include_guard = "_RELIBC_UNISTD_H"
 trailer = """
 #include <bits/fcntl.h>

src/header/utime/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = ["sys/types.h"]
+sys_includes = ["sys/types.h", "features.h"]
 include_guard = "_RELIBC_UTIME_H"
 language = "C"
 style = "Tag"

src/header/wchar/cbindgen.toml

@@ -1,4 +1,4 @@
-sys_includes = ["stddef.h", "stdint.h", "stdio.h", "time.h", "bits/wchar.h"]
+sys_includes = ["stddef.h", "stdint.h", "stdio.h", "time.h", "bits/wchar.h", "features.h"]
 include_guard = "_RELIBC_WCHAR_H"
 language = "C"
 style = "Type"

tests/Makefile

@@ -19,6 +19,7 @@ EXPECT_NAMES=\
 	error \
 	fcntl/create \
 	fcntl/fcntl \
+	features \
 	fnmatch \
 	futimens \
 	libgen \

tests/ctype.c

@@ -301,6 +301,8 @@ size_t num_test_cases = sizeof(test_cases) / sizeof(struct test_case);
 int main(void) {
     int retval = EXIT_SUCCESS;
 
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
     for(size_t i = 0; i < num_test_cases; ++i) {
         struct test_case tc = test_cases[i];
         CHECK_TEST(tc, isalnum, retval);
@@ -320,6 +322,7 @@ int main(void) {
         CHECK_TEST(tc, tolower, retval);
         CHECK_TEST(tc, toupper, retval);
     }
+    #pragma GCC diagnostic pop
 
     if (retval == EXIT_SUCCESS) {
         printf("Success: %d\n", retval);

tests/features.c

@@ -0,0 +1,39 @@
+// These tests are primarily to ensure the macros compile without 
+// causing any funny business.
+
+#include <features.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+__deprecated
+static void legacy(void) {}
+
+__deprecatedNote("Sometimes deletes user's home (oops); use foobar")
+static void legacy_notes(void) {}
+
+__nodiscard
+static uint8_t the_answer(void) {
+    return 42;
+}
+
+// GCC bug
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wattributes"
+__noreturn
+static void foobar(void) {
+    exit(0);
+}
+#pragma GCC diagnostic pop
+
+int main(void) {
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+    legacy();
+    legacy_notes();
+    #pragma GCC diagnostic pop
+    const int answer = the_answer();
+    char buf[40] = {0};
+    sprintf(buf, "Hey, -Werror, I'm using answer: %d\n", answer);
+    foobar();
+}

tests/futimens.c

@@ -42,7 +42,10 @@ int main(void) {
     exit(1);
   }
 
+  #pragma GCC diagnostic push
+  #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
   strncat(path, mktemp(temp), sizeof(temp));
+  #pragma GCC diagnostic pop
   strncat(path, file, sizeof(file));
   if (mkdir(temp, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH) != 0) {
     fprintf(stderr, "mkdir %s: %s\n", temp, strerror(errno));

tests/mkfifo.c

@@ -18,7 +18,11 @@ int main(void) {
     exit(1);
   }
 
+
+  #pragma GCC diagnostic push
+  #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
   path = strncat(path, mktemp(temp), sizeof(temp));
+  #pragma GCC diagnostic pop
   path = strncat(path, file, sizeof(file));
   if (mkdir(temp, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH) != 0) {
     fprintf(stderr, "mkdir %s: %s\n", temp, strerror(errno));

tests/mknod.c

@@ -18,10 +18,13 @@ int main(void) {
     exit(1);
   }
 
+  #pragma GCC diagnostic push
+  #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
   if(!mktemp(temp)) {
     fprintf(stderr, "Unable to create a unique dir name %s: %s\n", temp, strerror(errno));
     exit(1);
   }
+  #pragma GCC diagnostic pop
 
   path = strncat(path, temp, strlen(temp));
   path = strncat(path, file, strlen(file));

tests/mknodat.c

@@ -19,10 +19,13 @@ int main(void) {
     exit(1);
   }
 
+  #pragma GCC diagnostic push
+  #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
   if(!mktemp(temp)) {
     fprintf(stderr, "Unable to create a unique dir name %s: %s\n", temp, strerror(errno));
     exit(1);
   }
+  #pragma GCC diagnostic pop
 
   if (mkdir(temp, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH) != 0) {
     fprintf(stderr, "mkdir %s: %s\n", temp, strerror(errno));

tests/run_tests.sh

@@ -21,6 +21,7 @@ EXPECT_NAMES=(\
 	error \
 	fcntl/create \
 	fcntl/fcntl \
+    features \
 	fnmatch \
 	futimens \
 	libgen \
@@ -205,4 +206,4 @@ STATUS_NAMES=(\
 EXPECT_BINS=(${EXPECT_NAMES[@]/#/.\/bins_static\/})
 STATUS_BINS=(${STATUS_NAMES[@]/#/-s.\/bins_static\/})
 
-bins_verify/relibc-tests ${STATUS_BINS[@]} ${EXPECT_BINS[@]}
+bins_verify/relibc-tests ${STATUS_BINS[@]} ${EXPECT_BINS[@]}

tests/stdlib/alloc.c

@@ -182,6 +182,9 @@ int main(void) {
     test_cannot_alloc(ptr_reallocarray_maxsize, reallocarray_errno);
     free(ptr_reallocarray_maxsize);
     
+    // Warning for deprecated functions is expected so silence -Werror
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
     errno = 0;
     char * ptr_memalign_size0 = (char *)memalign(aligned_alloc_alignment, zero_size);
     int memalign_size0_errno = errno;
@@ -219,6 +222,8 @@ int main(void) {
     printf("memalign (alignment 3): ");
     test_invalid_aligned(ptr_memalign_align3, memalign_align3_errno);
     free(ptr_memalign_align3);
+
+    #pragma GCC diagnostic pop
     
     errno = 0;
     char * ptr_aligned_alloc_goodsize = (char *)aligned_alloc(aligned_alloc_alignment, aligned_alloc_goodsize);
@@ -234,6 +239,10 @@ int main(void) {
     test_invalid_aligned(ptr_aligned_alloc_badsize, aligned_alloc_badsize_errno);
     free(ptr_aligned_alloc_badsize);
     
+    // Warning for deprecated functions is expected so silence -Werror
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+
     errno = 0;
     char * ptr_valloc_size0 = (char *)valloc(zero_size);
     int valloc_size0_errno = errno;
@@ -289,4 +298,6 @@ int main(void) {
     printf("posix_memalign (SIZE_MAX): ");
     test_cannot_alloc(ptr_posix_memalign_maxsize, posix_memalign_maxsize_return);
     free(ptr_posix_memalign_maxsize);
+
+    #pragma GCC diagnostic pop
 }

tests/stdlib/mktemp.c

@@ -7,7 +7,10 @@
 int main(void) {
     char* string = (char*) calloc(20, sizeof(char));
     strcpy(string, "tempXXXXXX");
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
     mktemp(string);
+    #pragma GCC diagnostic pop
     printf("%s\n",string);
     free(string);
 }