Reapply "recipes ask whether a header is there instead of inferring it from the platform"

This reverts commit 75f5313.

Author: Sunrisepeak

pkgs/c/compat.c-ares.lua

@@ -1030,7 +1030,9 @@ package = {
 #define HAVE_BOOL_T
 
 /* Define to 1 if you have the clock_gettime function and monotonic timer. */
-/* #undef HAVE_CLOCK_GETTIME_MONOTONIC */
+#if __has_include(<time.h>) && !defined(_WIN32)
+#define HAVE_CLOCK_GETTIME_MONOTONIC 1
+#endif
 
 /* Define to 1 if you have the closesocket function. */
 #define HAVE_CLOSESOCKET
@@ -1087,7 +1089,12 @@ package = {
 /* #undef HAVE_GETSERVBYPORT_R */
 
 /* Define to 1 if you have the `gettimeofday' function. */
-/* #undef HAVE_GETTIMEOFDAY */
+/* SUB-SECOND TIME. `ares_timeval.c:93` refuses a configuration that names no
+ * source of it, and the Win32 one (`GetTickCount64`) needs `windows.h`. A
+ * POSIX-presenting target has `clock_gettime`, which `time.h` declares. */
+#if __has_include(<time.h>) && !defined(_WIN32)
+#define HAVE_GETTIMEOFDAY 1
+#endif
 
 /* Define to 1 if you have the `if_indextoname' function. */
 /* #undef HAVE_IF_INDEXTONAME */
@@ -1205,10 +1212,22 @@ package = {
 #define HAVE_STDLIB_H
 
 /* Define to 1 if you have the strcasecmp function. */
-/* #undef HAVE_STRCASECMP */
+/* WIN32 CRT NAMES vs POSIX NAMES, decided by what the C environment
+ * presents rather than by the platform. This block is the Windows branch of a
+ * recipe that branches on the PLATFORM; over openkal the target is PE and the
+ * C environment is POSIX, so the CRT spellings are the ones that are absent.
+ * `__has_builtin` cannot answer for library functions, so these ask the same
+ * question the headers do: `strings.h` carries the POSIX pair. */
+#if __has_include(<strings.h>)
+#define HAVE_STRCASECMP 1
+#define HAVE_STRNCASECMP 1
+#endif
+/* #undef HAVE_STRCASECMP_ORIGINAL */
 
 /* Define to 1 if you have the strcmpi function. */
+#if !__has_include(<strings.h>)
 #define HAVE_STRCMPI
+#endif
 
 /* Define to 1 if you have the strdup function. */
 #define HAVE_STRDUP
@@ -1229,7 +1248,9 @@ package = {
 /* #undef HAVE_STRNCMPI */
 
 /* Define to 1 if you have the strnicmp function. */
+#if !__has_include(<strings.h>)
 #define HAVE_STRNICMP
+#endif
 
 /* Define to 1 if you have the <stropts.h> header file. */
 /* #undef HAVE_STROPTS_H */
@@ -1276,23 +1297,42 @@ package = {
 /* Define to 1 if you have the <time.h> header file. */
 #define HAVE_TIME_H
 
-/* Define to 1 if you have the <unistd.h> header file. */
-/* #undef HAVE_UNISTD_H */
-
-/* Define to 1 if you have the windows.h header file. */
+/* THESE ASK WHETHER A HEADER IS THERE, SO THEY ASK THE COMPILER.
+ *
+ * This block is the Windows branch of a recipe that branches on the PLATFORM,
+ * and it used to define all four unconditionally. That was true of every
+ * Windows target this index had until a C library began presenting POSIX on
+ * one: over openkal the target is still PE, still Win64, and there is no
+ * `windows.h` --- `ares_setup.h:81` then reached for it and this repository's
+ * own compatibility measurement recorded
+ *
+ *     ares_setup.h:81:12: fatal error: 'windows.h' file not found
+ *
+ * `__has_include` is standard C and asks the question actually being asked.
+ * `HAVE_UNISTD_H` gets the same treatment for the same reason, from the other
+ * side: a POSIX-presenting Windows target HAS it. */
+#if __has_include(<unistd.h>)
+#define HAVE_UNISTD_H 1
+#endif
+
+#if __has_include(<windows.h>)
 #define HAVE_WINDOWS_H
+#endif
 
-/* Define to 1 if you have the winsock2.h header file. */
+#if __has_include(<winsock2.h>)
 #define HAVE_WINSOCK2_H
+#endif
 
-/* Define to 1 if you have the winsock.h header file. */
+#if __has_include(<winsock.h>)
 #define HAVE_WINSOCK_H
+#endif
 
 /* Define to 1 if you have the writev function. */
 /* #undef HAVE_WRITEV */
 
-/* Define to 1 if you have the ws2tcpip.h header file. */
+#if __has_include(<ws2tcpip.h>)
 #define HAVE_WS2TCPIP_H
+#endif
 
 /* Define if __system_property_get exists. */
 /* #undef HAVE___SYSTEM_PROPERTY_GET */

pkgs/c/compat.curl.lua

@@ -248,20 +248,56 @@ package = {
 #if defined(__linux__)
 
 #define CURL_OS "Linux"
-/* glibc's strerror_r returns char*, not int — curl needs to know which */
+
+/* `__linux__` ANSWERS "WHICH KERNEL", NOT "WHICH USERSPACE IS INSTALLED", and
+ * this block used to read it as the second. Every entry below that names a
+ * HEADER now asks whether that header is reachable, which is the question
+ * being asked and is standard C; every entry that names a GLIBC extension
+ * asks for glibc.
+ *
+ * Measured: over openkal-musl on x86_64-linux-gnu the kernel is Linux, so
+ * `__linux__` is correct, and `#define HAVE_LINUX_TCP_H 1` then sent
+ * `lib/setopt.c:31` to a uapi header that C library does not carry ---
+ * `fatal error: 'linux/tcp.h' file not found`, one of the failures in this
+ * repository's own compatibility measurement. */
+#if __has_include(<linux/tcp.h>)
+#define HAVE_LINUX_TCP_H 1
+#endif
+/* `__has_include` ANSWERS ABOUT THE HEADER, NOT ABOUT THE FUNCTION, and those
+ * two come apart here. openkal-musl CARRIES `sys/eventfd.h` and declares
+ * `eventfd` absent in its `[c-abi-absent]` table, so defining `HAVE_EVENTFD`
+ * from the header's presence produced a link that mcpp explained by name:
+ *
+ *     the C library in this graph (musl) declares that it does not supply
+ *     the following, and the link has just asked for it:
+ *       eventfd              as timerfd_create
+ *
+ * Neither is declared: curl has a poll-based path and takes it. A header
+ * test cannot stand in for a symbol test. */
+#if __has_include(<termio.h>)
+#define HAVE_TERMIO_H 1
+#endif
+#if __has_include(<sys/xattr.h>)
+#define HAVE_FSETXATTR 1
+#define HAVE_FSETXATTR_5 1
+#endif
+
+/* WHICH `strerror_r`, AND EXACTLY ONE OF THEM. glibc's returns `char*`,
+ * POSIX's returns `int`, and `strerr.c:30` refuses a configuration that names
+ * neither or both. Asking `__linux__` answered "glibc" for musl, which is the
+ * wrong one; leaving it out answered "neither", which is also refused. */
+#if defined(__GLIBC__)
 #define HAVE_GLIBC_STRERROR_R 1
+#else
+#define HAVE_POSIX_STRERROR_R 1
+#endif
+
 #define HAVE_GETHOSTBYNAME_R 1
 #define HAVE_GETHOSTBYNAME_R_6 1
 #define HAVE_ACCEPT4 1
 #define HAVE_PIPE2 1
-#define HAVE_EVENTFD 1
-#define HAVE_SYS_EVENTFD_H 1
 #define HAVE_SENDMMSG 1
 #define HAVE_MEMRCHR 1
-#define HAVE_FSETXATTR 1
-#define HAVE_FSETXATTR_5 1
-#define HAVE_LINUX_TCP_H 1
-#define HAVE_TERMIO_H 1
 #define HAVE_CLOCK_GETTIME_MONOTONIC_RAW 1
 /* Debian/Fedora layout; overridable at runtime with CURLOPT_CAINFO or the
  * SSL_CERT_FILE environment variable. */