sanity: add libc/stdlib sanity checks

These are meant to test our back-compat stubs, but they are enabled for all
builds for the sake of consistency.

src/Makefile.am

@@ -85,7 +85,8 @@ BITCOIN_CORE_H = \
   util.h \
   version.h \
   walletdb.h \
-  wallet.h
+  wallet.h \
+  compat/sanity.h
 
 JSON_H = \
   json/json_spirit.h \
@@ -154,6 +155,8 @@ libbitcoin_common_a_SOURCES = \
   sync.cpp \
   util.cpp \
   version.cpp \
+  compat/glibc_sanity.cpp \
+  compat/glibcxx_sanity.cpp \
   $(BITCOIN_CORE_H)
 
 if GLIBC_BACK_COMPAT

src/compat/glibc_sanity.cpp

@@ -0,0 +1,61 @@
+#include "bitcoin-config.h"
+
+#include <cstddef>
+#if defined(HAVE_SYS_SELECT_H)
+#include <sys/select.h>
+#endif
+
+extern "C" void* memcpy(void* a, const void* b, size_t c);
+void* memcpy_int(void* a, const void* b, size_t c)
+{
+  return memcpy(a,b,c);
+}
+
+namespace {
+// trigger: Use the memcpy_int wrapper which calls our internal memcpy.
+//   A direct call to memcpy may be optimized away by the compiler.
+// test: Fill an array with a sequence of integers. memcpy to a new empty array.
+//   Verify that the arrays are equal. Use an odd size to decrease the odds of
+//   the call being optimized away.
+template <unsigned int T>
+bool sanity_test_memcpy()
+{
+    unsigned int memcpy_test[T];
+    unsigned int memcpy_verify[T] = {};
+    for (unsigned int i = 0; i != T; ++i)
+        memcpy_test[i] = i;
+
+    memcpy_int(memcpy_verify,memcpy_test,sizeof(memcpy_test));
+
+    for (unsigned int i = 0; i != T; ++i)
+    {
+        if(memcpy_verify[i] != i)
+            return false;
+    }
+    return true;
+}
+
+#if defined(HAVE_SYS_SELECT_H)
+// trigger: Call FD_SET to trigger __fdelt_chk. FORTIFY_SOURCE must be defined
+//   as >0 and optimizations must be set to at least -O2.
+// test: Add a file descriptor to an empty fd_set. Verify that it has been
+//   correctly added.
+bool sanity_test_fdelt()
+{
+    fd_set fds;
+    FD_ZERO(&fds);
+    FD_SET(0, &fds);
+    return FD_ISSET(0,&fds);
+}
+#endif
+
+} // anon namespace
+
+bool glibc_sanity_test()
+{
+#if defined(HAVE_SYS_SELECT_H)
+    if (!sanity_test_fdelt())
+        return false;
+#endif
+    return sanity_test_memcpy<1025>();
+}

src/compat/glibcxx_sanity.cpp

@@ -0,0 +1,61 @@
+#include <locale>
+#include <list>
+#include <stdexcept>
+
+namespace{
+
+// trigger: use ctype<char>::widen to trigger ctype<char>::_M_widen_init().
+// test: convert a char from narrow to wide and back. Verify that the result
+//   matches the original.
+bool sanity_test_widen(char testchar)
+{
+    const std::ctype<char>& test(std::use_facet< std::ctype<char> >(std::locale()));
+    return test.narrow(test.widen(testchar),'b') == testchar;
+}
+
+// trigger: use list::push_back and list::pop_back to trigger _M_hook and
+//   _M_unhook.
+// test: Push a sequence of integers into a list. Pop them off and verify that
+//   they match the original sequence.
+bool sanity_test_list(unsigned int size)
+{
+    std::list<unsigned int> test;
+    for (unsigned int i = 0; i != size; ++i)
+        test.push_back(i+1);
+
+    if (test.size() != size)
+        return false;
+
+    while (!test.empty())
+    {
+        if(test.back() != test.size())
+            return false;
+        test.pop_back();
+    }
+    return true;
+}
+
+} // anon namespace
+
+// trigger: string::at(x) on an empty string to trigger __throw_out_of_range_fmt.
+// test: force std::string to throw an out_of_range exception. Verify that
+//   it's caught correctly.
+bool sanity_test_range_fmt()
+{
+    std::string test;
+    try
+    {
+        test.at(1);
+    }
+    catch (const std::out_of_range&)
+    {
+        return true;
+    }
+    catch (...){}
+    return false;
+}
+
+bool glibcxx_sanity_test()
+{
+    return sanity_test_widen('a') && sanity_test_list(100) && sanity_test_range_fmt();
+}

src/compat/sanity.h

@@ -0,0 +1,7 @@
+#ifndef BITCON_COMPAT_SANITY_H
+#define BITCON_COMPAT_SANITY_H
+
+bool glibc_sanity_test();
+bool glibcxx_sanity_test();
+
+#endif