Fix for handling absolute include paths

test/llvm_ir_correct/include-self.f90

@@ -0,0 +1,18 @@
+!
+! Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+! See https://llvm.org/LICENSE.txt for license information.
+! SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+!
+
+! RUN: %flang -cpp %s -DSELF=\"`realpath "%s"`\" -S -emit-llvm -o - | FileCheck %s
+
+#ifndef __SELF_INCLUDED
+#define __SELF_INCLUDED
+
+#include SELF
+
+subroutine foo
+! CHECK: foo
+end subroutine
+
+#endif

tools/flang1/flang1exe/accpp.c

@@ -2103,6 +2103,7 @@ add_to_incllist(char *fullname)
 static void
 _doincl(char *name, int type, LOGICAL include_next)
 {
+  FILE *tmpfp;
   char fullname[MAX_PATHNAME_LEN];
   int i;
 
@@ -2130,6 +2131,16 @@ _doincl(char *name, int type, LOGICAL include_next)
       goto found;
     }
 
+  if (type == 0) { /* could be absolute path, check where it leads to */
+    tmpfp = fopen(name, "r");
+    if (tmpfp) {
+      snprintf(fullname, MAX_PATHNAME_LEN, "%s", name);
+      idir.last = 0;
+      if (fclose(tmpfp) == 0)
+        goto found;
+    }
+  }
+
   pperror(206, name, 4); /* cpp just continues, but why?? */
   return;
 

tools/flang1/flang1exe/fpp.c

@@ -1115,6 +1115,7 @@ dodef(void)
 static void
 doincl(LOGICAL include_next)
 {
+  FILE *tmpfp;
   int toktyp;
   char buff[MAX_FNAME_LEN];
   char fullname[MAX_FNAME_LEN];
@@ -1178,6 +1179,16 @@ doincl(LOGICAL include_next)
       goto found;
     }
 
+  if (type == 0) { /* could be absolute path, check where it leads to */
+    tmpfp = fopen(buff, "r");
+    if (tmpfp) {
+      snprintf(fullname, MAX_FNAME_LEN, "%s", buff);
+      idir.last = 0;
+      if (fclose(tmpfp) == 0)
+        goto found;
+    }
+  }
+
   pperror(226, buff, 4); /* cpp just continues, but why?? */
   return;