Add chibicc

This program popped up on Hacker News recently. It's the only modern
compiler I've ever seen that doesn't have dependencies and is easily
modified. So I added all of the missing GNU extensions I like to use
which means it might be possible soon to build on non-Linux and have
third party not vendor gcc binaries.

third_party/chibicc/test/unicode_test.c

@@ -0,0 +1,138 @@
+#include "third_party/chibicc/test/test.h"
+
+/* TODO(jart): shl overflow in read_escaped_char */
+
+#define STR(x) #x
+
+typedef unsigned short char16_t;
+typedef unsigned int char32_t;
+typedef int wchar_t;
+
+int π = 3;
+
+int main() {
+  ASSERT(4, sizeof(L'\0'));
+  ASSERT(97, L'a');
+
+  ASSERT(0, strcmp("αβγ", "\u03B1\u03B2\u03B3"));
+  ASSERT(0, strcmp("日本語", "\u65E5\u672C\u8A9E"));
+  ASSERT(0, strcmp("日本語", "\U000065E5\U0000672C\U00008A9E"));
+  ASSERT(0, strcmp("🌮", "\U0001F32E"));
+
+  ASSERT(-1, L'\xffffffff' >> 31);
+  ASSERT(946, L'β');
+  ASSERT(12354, L'あ');
+  ASSERT(127843, L'🍣');
+
+  ASSERT(2, sizeof(u'\0'));
+  ASSERT(1, u'\xffff' >> 15);
+  ASSERT(97, u'a');
+  ASSERT(946, u'β');
+  ASSERT(12354, u'あ');
+  ASSERT(62307, u'🍣');
+
+  ASSERT(0, strcmp(STR(u'a'), "u'a'"));
+
+  ASSERT(4, sizeof(U'\0'));
+  ASSERT(1, U'\xffffffff' >> 31);
+  ASSERT(97, U'a');
+  ASSERT(946, U'β');
+  ASSERT(12354, U'あ');
+  ASSERT(127843, U'🍣');
+
+  ASSERT(0, strcmp(STR(U'a'), "U'a'"));
+
+  ASSERT(4, sizeof(u8"abc"));
+  ASSERT(0, strcmp(u8"abc", "abc"));
+
+  ASSERT(0, strcmp(STR(u8"a"), "u8\"a\""));
+
+  ASSERT(2, sizeof(u""));
+  ASSERT(10, sizeof(u"\xffzzz"));
+  ASSERT(0, memcmp(u"", "\0\0", 2));
+  ASSERT(0, memcmp(u"abc", "a\0b\0c\0\0\0", 8));
+  ASSERT(0, memcmp(u"日本語", "\345e,g\236\212\0\0", 8));
+  ASSERT(0, memcmp(u"🍣", "<\330c\337\0\0", 6));
+  ASSERT(u'β', u"βb"[0]);
+  ASSERT(u'b', u"βb"[1]);
+  ASSERT(0, u"βb"[2]);
+
+  ASSERT(0, strcmp(STR(u"a"), "u\"a\""));
+
+  ASSERT(4, sizeof(U""));
+  ASSERT(20, sizeof(U"\xffzzz"));
+  ASSERT(0, memcmp(U"", "\0\0\0\0", 4));
+  ASSERT(0, memcmp(U"abc", "a\0\0\0b\0\0\0c\0\0\0\0\0\0\0", 16));
+  ASSERT(0, memcmp(U"日本語", "\345e\0\0,g\0\0\236\212\0\0\0\0\0\0", 16));
+  ASSERT(0, memcmp(U"🍣", "c\363\001\0\0\0\0\0", 8));
+  ASSERT(u'β', U"βb"[0]);
+  ASSERT(u'b', U"βb"[1]);
+  ASSERT(0, U"βb"[2]);
+  ASSERT(1, U"\xffffffff"[0] >> 31);
+
+  ASSERT(0, strcmp(STR(U"a"), "U\"a\""));
+
+  ASSERT(4, sizeof(L""));
+  ASSERT(20, sizeof(L"\xffzzz"));
+  ASSERT(0, memcmp(L"", "\0\0\0\0", 4));
+  ASSERT(0, memcmp(L"abc", "a\0\0\0b\0\0\0c\0\0\0\0\0\0\0", 16));
+  ASSERT(0, memcmp(L"日本語", "\345e\0\0,g\0\0\236\212\0\0\0\0\0\0", 16));
+  ASSERT(0, memcmp(L"🍣", "c\363\001\0\0\0\0\0", 8));
+  ASSERT(u'β', L"βb"[0]);
+  ASSERT(u'b', L"βb"[1]);
+  ASSERT(0, L"βb"[2]);
+  ASSERT(-1, L"\xffffffff"[0] >> 31);
+
+  ASSERT(0, strcmp(STR(L"a"), "L\"a\""));
+
+  ASSERT(u'α', ({
+           char16_t x[] = u"αβ";
+           x[0];
+         }));
+  ASSERT(u'β', ({
+           char16_t x[] = u"αβ";
+           x[1];
+         }));
+  ASSERT(6, ({
+           char16_t x[] = u"αβ";
+           sizeof(x);
+         }));
+
+  ASSERT(U'🤔', ({
+           char32_t x[] = U"🤔x";
+           x[0];
+         }));
+  ASSERT(U'x', ({
+           char32_t x[] = U"🤔x";
+           x[1];
+         }));
+  ASSERT(12, ({
+           char32_t x[] = U"🤔x";
+           sizeof(x);
+         }));
+
+  ASSERT(L'🤔', ({
+           wchar_t x[] = L"🤔x";
+           x[0];
+         }));
+  ASSERT(L'x', ({
+           wchar_t x[] = L"🤔x";
+           x[1];
+         }));
+  ASSERT(12, ({
+           wchar_t x[] = L"🤔x";
+           sizeof(x);
+         }));
+
+  ASSERT(3, π);
+  ASSERT(3, ({
+           int あβ0¾ = 3;
+           あβ0¾;
+         }));
+  ASSERT(5, ({
+           int $$$ = 5;
+           $$$;
+         }));
+
+  return 0;
+}