Add additional handling for AddressSanitizer

This commit is a continuation of commit 2230e3e ("ignore sanitizer"),
which added the "no_sanitize_address" attribute to ctest_main to
prevent ASan from flagging reads while discovering the registered test
structs.  Clang's ASan implementation adds a redzone around globals, so
some additional handling is required.

Starting with clang 4.0, the "no_sanitize_address" can also be applied
to globals to inhibit creating the globals redzone.  However, for
earlier versions of clang (3.1 was the first to include ASan), we need
to work around the redzone.  Thanks to ASAN_UNPOISON_MEMORY_REGION(),
this is possible.  By unpoisoning the memory region and skipping over
any alignment padding, we are able to derive the test list, but the
"magic" value is now required to bookend the ctest struct.

This commit also attempts to make the compiler platform and version
checking logic more readable.

ctest.h

@@ -23,36 +23,73 @@
 #endif
 
 #include <inttypes.h> /* intmax_t, uintmax_t, PRI* */
-#include <stddef.h> /* size_t */
+#include <stddef.h> /* size_t, offsetof */
 
 typedef void (*ctest_setup_func)(void*);
 typedef void (*ctest_teardown_func)(void*);
 
 #define CTEST_IMPL_PRAGMA(x) _Pragma (#x)
 
-#if defined(__GNUC__)
-#if defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
+#define CTEST_IMPL_COMPILER_MINIMUM_VERSION(exp_major, exp_minor, \
+                                            real_major, real_minor) \
+    (((real_major) > (exp_major)) \
+     || ((real_major) == (exp_major) && (real_minor) >= (exp_minor)))
+
+#if defined(__GNUC__) && !defined(__clang__)
+#   define CTEST_IMPL_GCC_MINIMUM_VERSION(major, minor) \
+        CTEST_IMPL_COMPILER_MINIMUM_VERSION(major, minor, \
+                                            __GNUC__, __GNUC_MINOR__)
+#else
+#   define CTEST_IMPL_GCC_MINIMUM_VERSION(major, minor) 0
+#endif
+
+#ifdef __clang__
+#   define CTEST_IMPL_CLANG_MINIMUM_VERSION(major, minor) \
+        CTEST_IMPL_COMPILER_MINIMUM_VERSION(major, minor, \
+                                            __clang_major__, __clang_minor__)
+#else
+#   define CTEST_IMPL_CLANG_MINIMUM_VERSION(major, minor) 0
+#endif
+
+#if CTEST_IMPL_GCC_MINIMUM_VERSION(4, 6) || defined(__clang__)
 /* the GCC argument will work for both gcc and clang  */
 #define CTEST_IMPL_DIAG_PUSH_IGNORED(w) \
     CTEST_IMPL_PRAGMA(GCC diagnostic push) \
     CTEST_IMPL_PRAGMA(GCC diagnostic ignored "-W" #w)
 #define CTEST_IMPL_DIAG_POP() \
     CTEST_IMPL_PRAGMA(GCC diagnostic pop)
-#else
+#elif defined(__GNUC__)
 /* the push/pop functionality wasn't in gcc until 4.6, fallback to "ignored"  */
 #define CTEST_IMPL_DIAG_PUSH_IGNORED(w) \
     CTEST_IMPL_PRAGMA(GCC diagnostic ignored "-W" #w)
 #define CTEST_IMPL_DIAG_POP()
-#endif
 #else
 /* leave them out entirely for non-GNUC compilers  */
 #define CTEST_IMPL_DIAG_PUSH_IGNORED(w)
 #define CTEST_IMPL_DIAG_POP()
 #endif
 
+#if CTEST_IMPL_GCC_MINIMUM_VERSION(4, 8)
+#   define CTEST_IMPL_NO_ASAN_FUNCTION __attribute__ ((no_sanitize_address))
+#   define CTEST_IMPL_NO_ASAN_VARIABLE
+#elif CTEST_IMPL_CLANG_MINIMUM_VERSION(4, 0)
+#   define CTEST_IMPL_NO_ASAN_FUNCTION __attribute__ ((no_sanitize_address))
+#   define CTEST_IMPL_NO_ASAN_VARIABLE __attribute__ ((no_sanitize_address))
+#elif CTEST_IMPL_CLANG_MINIMUM_VERSION(3, 1) && __has_feature(address_sanitizer)
+#   warning "Clang 3.x AddressSanitizer may interfere with ctest, proceed with caution!"
+#   define CTEST_IMPL_NO_ASAN_FUNCTION __attribute__ ((no_sanitize_address))
+#   define CTEST_IMPL_NO_ASAN_VARIABLE
+#   define CTEST_IMPL_CLANG_POISIONED_GLOBALS
+#else
+#   define CTEST_IMPL_NO_ASAN_FUNCTION
+#   define CTEST_IMPL_NO_ASAN_VARIABLE
+#endif
+
 CTEST_IMPL_DIAG_PUSH_IGNORED(strict-prototypes)
 
 struct ctest {
+    unsigned int magic1; // must be first!
+
     const char* ssname;  // suite name
     const char* ttname;  // test name
     void (*run)();
@@ -63,7 +100,7 @@ struct ctest {
 
     int skip;
 
-    unsigned int magic;
+    unsigned int magic2; // must be last!
 };
 
 CTEST_IMPL_DIAG_POP()
@@ -86,15 +123,19 @@ CTEST_IMPL_DIAG_POP()
 #endif
 
 #define CTEST_IMPL_STRUCT(sname, tname, tskip, tdata, tsetup, tteardown) \
-    static struct ctest CTEST_IMPL_TNAME(sname, tname) CTEST_IMPL_SECTION = { \
+    CTEST_IMPL_NO_ASAN_VARIABLE \
+    CTEST_IMPL_SECTION \
+    static struct ctest CTEST_IMPL_TNAME(sname, tname) = { \
+        .magic1 = CTEST_IMPL_MAGIC, \
         .ssname=#sname, \
         .ttname=#tname, \
         .run = CTEST_IMPL_FNAME(sname, tname), \
         .data = tdata, \
         .setup = (ctest_setup_func*) tsetup, \
         .teardown = (ctest_teardown_func*) tteardown, \
         .skip = tskip, \
-        .magic = CTEST_IMPL_MAGIC }
+        .magic2 = CTEST_IMPL_MAGIC, \
+    }
 
 #define CTEST_SETUP(sname) \
     static void CTEST_IMPL_SETUP_FNAME(sname)(struct CTEST_IMPL_DATA_SNAME(sname)* data); \
@@ -188,12 +229,13 @@ void assert_dbl_far(double exp, double real, double tol, const char* caller, int
 
 #include <setjmp.h>
 #include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <sys/time.h>
 #include <unistd.h>
-#include <stdint.h>
-#include <stdlib.h>
 #include <wchar.h>
 
 static size_t ctest_errorsize;
@@ -449,9 +491,42 @@ static void sighandler(int signum)
 }
 #endif
 
-int ctest_main(int argc, const char *argv[]);
+#ifdef CTEST_IMPL_CLANG_POISIONED_GLOBALS
+#include <sanitizer/asan_interface.h>
+#endif
+
+static struct ctest* ctest_impl_adjacent(const struct ctest* test,
+                                         int direction, size_t offset)
+{
+    const volatile unsigned int* magic = (const unsigned int*)
+                                         ((const char*)
+                                          (test + direction) + offset);
+
+#if CTEST_IMPL_POISIONED_GLOBALS
+    while (ASAN_UNPOISON_MEMORY_REGION(magic, sizeof(*magic)), *magic == 0) {
+        magic += direction;
+    }
+#endif
+
+CTEST_IMPL_DIAG_PUSH_IGNORED(cast-qual)
+    return *magic == CTEST_IMPL_MAGIC ? (struct ctest*)
+                                        ((char*)magic - offset)
+                                      : NULL;
+CTEST_IMPL_DIAG_POP()
+}
 
-__attribute__((no_sanitize_address)) int ctest_main(int argc, const char *argv[])
+static struct ctest* ctest_impl_next(const struct ctest* test)
+{
+    return ctest_impl_adjacent(test, 1, offsetof(struct ctest, magic1));
+}
+
+static struct ctest* ctest_impl_prev(const struct ctest* test)
+{
+    return ctest_impl_adjacent(test, -1, offsetof(struct ctest, magic2));
+}
+
+CTEST_IMPL_NO_ASAN_FUNCTION
+int ctest_main(int argc, const char *argv[])
 {
     static int total = 0;
     static int num_ok = 0;
@@ -476,27 +551,19 @@ __attribute__((no_sanitize_address)) int ctest_main(int argc, const char *argv[]
     uint64_t t1 = getCurrentTime();
 
     struct ctest* ctest_begin = &CTEST_IMPL_TNAME(suite, test);
-    struct ctest* ctest_end = &CTEST_IMPL_TNAME(suite, test);
-    // find begin and end of section by comparing magics
-    while (1) {
-        struct ctest* t = ctest_begin-1;
-        if (t->magic != CTEST_IMPL_MAGIC) break;
-        ctest_begin--;
-    }
     while (1) {
-        struct ctest* t = ctest_end+1;
-        if (t->magic != CTEST_IMPL_MAGIC) break;
-        ctest_end++;
+        struct ctest* t = ctest_impl_prev(ctest_begin);
+        if (t == NULL) break;
+        ctest_begin = t;
     }
-    ctest_end++;    // end after last one
 
     static struct ctest* test;
-    for (test = ctest_begin; test != ctest_end; test++) {
+    for (test = ctest_begin; test != NULL; test = ctest_impl_next(test)) {
         if (test == &CTEST_IMPL_TNAME(suite, test)) continue;
         if (filter(test)) total++;
     }
 
-    for (test = ctest_begin; test != ctest_end; test++) {
+    for (test = ctest_begin; test != NULL; test = ctest_impl_next(test)) {
         if (test == &CTEST_IMPL_TNAME(suite, test)) continue;
         if (filter(test)) {
             ctest_errorbuffer[0] = 0;