preproc: add %ifenv

Add %ifenv to test for the presence of an environment variable.  The
environment variable can, but does not have to be, prefixed with %!.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

2 files changed, 23 insertions, 1 deletions

diff --git a/pptok.dat b/pptok.dat
index 76ca3609..b78d138a 100644
--- a/pptok.dat
+++ b/pptok.dat
@@ -1,6 +1,6 @@
 ## --------------------------------------------------------------------------
 ##   
-##   Copyright 1996-2009 The NASM Authors - All Rights Reserved
+##   Copyright 1996-2010 The NASM Authors - All Rights Reserved
 ##   See the file AUTHORS included with the NASM distribution for
 ##   the specific copyright holders.
 ##
@@ -39,6 +39,7 @@
 *ctx
 *def
 *empty
+*env
 *id
 *idn
 *idni
diff --git a/preproc.c b/preproc.c
index cc5034f3..ba1acd55 100644
--- a/preproc.c
+++ b/preproc.c
@@ -1610,6 +1610,7 @@ static bool if_condition(Token * tline, enum preproc_token ct)
     struct tokenval tokval;
     expr *evalresult;
     enum pp_token_type needtype;
+    const char *p;
 
     origline = tline;
 
@@ -1649,6 +1650,26 @@ static bool if_condition(Token * tline, enum preproc_token ct)
         }
         break;
 
+    case PPC_IFENV:
+	tline = expand_smacro(tline);
+        j = false;              /* have we matched yet? */
+        while (tline) {
+            skip_white_(tline);
+            if (!tline || (tline->type != TOK_ID &&
+                           (tline->type != TOK_PREPROC_ID ||
+			       tline->text[1] != '!'))) {
+                error(ERR_NONFATAL,
+                      "`%s' expects environment variable names",
+		      pp_directives[ct]);
+                goto fail;
+            }
+	    p = tline->type == TOK_ID ? tline->text : tline->text + 2;
+	    if (getenv(p))
+		j = true;
+            tline = tline->next;
+        }
+        break;
+
     case PPC_IFIDN:
     case PPC_IFIDNI:
         tline = expand_smacro(tline);