create distinct interned string type

Interned strings are used pervasively, so it's a good idea to add a
layer of type safety to differentiate them from general cstrs and avoid
potential bugs from comparing non-interned and interned strings. Not
that that's happened so far that I can remember, but it could.

I'm 90% sure it's legal to alias `struct {char c;}` pointers with `char`
pointers. This specific typedef gives type safety but with a simple
one-way `internstr -> const char *` typecast (with `&istr->c`).
Converting the other way around is more intentional: a straight up cast
`(internstr)cstr` which sticks out as unchecked and probably wrong, or
calling the intern(cstr) function, which is the right way.

1 files changed, 3 insertions, 3 deletions

diff --git a/x86_64/emit.c b/x86_64/emit.c
index 3c72712..8a1673d 100644
--- a/x86_64/emit.c
+++ b/x86_64/emit.c
@@ -251,7 +251,7 @@ opermatch(enum operpat pat, struct oper oper)
 
 static bool usebp; /* use RBP? */
 static int rbpoff;
-static const char *curfnsym;
+static internstr curfnsym;
 static uchar *fnstart;
 
 /* Given an instruction description table, find the first entry that matches
@@ -334,7 +334,7 @@ encode(uchar **pcode, const struct desc *tab, int ntab, enum irclass k, struct o
             static uchar offs[NOPERENC] = { [EN_MI8] = 1, [EN_MI16] = 2, [EN_MI32] = 4 };
             uint addr;
             int disp = mem.disp - 4 - offs[en->operenc];
-            const char *sym = xcon2sym(mem.con);
+            internstr sym = xcon2sym(mem.con);
             B(/*mod 0*/ (reg & 7) << 3 | RBP);
             if (objhassym(sym, &addr) == Stext) {
                I32(addr - (*pcode - objout.textbegin) + disp);
@@ -433,7 +433,7 @@ encode(uchar **pcode, const struct desc *tab, int ntab, enum irclass k, struct o
       if (rex) B(0x40 | rex);
       D(opc, nopc);
       assert(dst.t == OSYM);
-      const char *sym = xcon2sym(dst.con);
+      internstr sym = xcon2sym(dst.con);
       uint addr;
       if (sym == curfnsym) {
          I32(fnstart - *pcode - 4);