Portability improvements (#1105)

* Move `raise` code to be behind an autoconf check

This moves the call to `raise` behind a `HAVE_RAISE` autoconf check,
in addition to `__wasm__`. This is intended to help porting to
other platforms that don't support `raise` (e.g. modern game consoles).

* Add autoconf check for `sysconf`

Only try to invoke `sysconf` if the target platform supports it, and
don't warn about unknown page size if `PAGE_SIZE` was defined. Add an
include for `sys/param.h` to increase likelihood of finding `PAGE_SIZE`.
This is intended to help porting to other platforms that don't support
`sysconf` (e.g. modern game consoles) that have a fixed hardware page
size.

* Don't try to use raise & sysconf in a WASI environment

Co-authored-by: Frank Denis <124872+jedisct1@users.noreply.github.com>

configure.ac

@@ -594,7 +594,7 @@ AC_SUBST(CFLAGS_AESNI)
 AC_SUBST(CFLAGS_PCLMUL)
 AC_SUBST(CFLAGS_RDRAND)
 
-AC_CHECK_HEADERS([sys/mman.h sys/random.h intrin.h sys/auxv.h])
+AC_CHECK_HEADERS([sys/mman.h sys/param.h sys/random.h intrin.h sys/auxv.h])
 
 AC_MSG_CHECKING([if _xgetbv() is available])
 AC_LINK_IFELSE(
@@ -820,8 +820,9 @@ AS_IF([test "x$EMSCRIPTEN" = "x"],[
   AC_CHECK_FUNCS([arc4random arc4random_buf])
   AS_IF([test "x$WASI" = "x"],[
     AC_CHECK_FUNCS([mmap mlock madvise mprotect])
+    AC_CHECK_FUNCS([raise])
+    AC_CHECK_FUNCS([sysconf])
   ])
-
   AC_MSG_CHECKING(for getrandom with a standard API)
   AC_LINK_IFELSE([AC_LANG_PROGRAM([[
 #include <stdlib.h>

src/libsodium/sodium/utils.c

@@ -9,7 +9,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#ifndef __wasm__
+#if defined(HAVE_RAISE) && !defined(__wasm__)
 # include <signal.h>
 #endif
 
@@ -17,6 +17,10 @@
 # include <sys/mman.h>
 #endif
 
+#ifdef HAVE_SYS_PARAM_H
+# include <sys/param.h>
+#endif
+
 #ifdef _WIN32
 # include <windows.h>
 # include <wincrypt.h>
@@ -402,7 +406,7 @@ int
 _sodium_alloc_init(void)
 {
 #ifdef HAVE_ALIGNED_MALLOC
-# if defined(_SC_PAGESIZE)
+# if defined(_SC_PAGESIZE) && defined(HAVE_SYSCONF)
     long page_size_ = sysconf(_SC_PAGESIZE);
     if (page_size_ > 0L) {
         page_size = (size_t) page_size_;
@@ -411,7 +415,7 @@ _sodium_alloc_init(void)
     SYSTEM_INFO si;
     GetSystemInfo(&si);
     page_size = (size_t) si.dwPageSize;
-# else
+# elif !defined(PAGE_SIZE)
 #  warning Unknown page size
 # endif
     if (page_size < CANARY_SIZE || page_size < sizeof(size_t)) {
@@ -503,7 +507,7 @@ _mprotect_readwrite(void *ptr, size_t size)
 __attribute__((noreturn)) static void
 _out_of_bounds(void)
 {
-# ifndef __wasm__
+# if defined(HAVE_RAISE) && !defined(__wasm__)
 #  ifdef SIGSEGV
     raise(SIGSEGV);
 #  elif defined(SIGKILL)