[gcc/devel/c++-modules] Fortran : get_environment_variable runtime error PR96486

[gcc/devel/c++-modules] Fortran : get_environment_variable runtime error PR96486

[Nathan Sidwell]

https://gcc.gnu.org/g:de09e7ebc9d5555653745a103eef2b20c7f1dd76

commit de09e7ebc9d5555653745a103eef2b20c7f1dd76
Author: Mark Eggleston <markeggleston@gcc.gnu.org>
Date:   Mon Aug 10 08:07:39 2020 +0100

    Fortran  :  get_environment_variable runtime error PR96486
    
    Runtime error occurs when the type of the value argument is
    character(0):  "Zero-length string passed as value...".
    The status argument, intent(out), will contain -1 if the value
    of the environment is too large to fit in the value argument, this
    is the case if the type is character(0) so there is no reason to
    produce a runtime error if the value argument is zero length.
    
    2020-08-24  Mark Eggleston  <markeggleston@gcc.gnu.org>
    
    libgfortran/
    
            PR fortran/96486
            * intrinsics/env.c: If value_len is > 0 blank the string.
            Copy the result only if its length is > 0.
    
    2020-08-24  Mark Eggleston  <markeggleston@gcc.gnu.org>
    
    gcc/testsuite/
    
            PR fortran/96486
            * gfortran.dg/pr96486.f90: New test.

Diff:
---
 gcc/testsuite/gfortran.dg/pr96486.f90 | 9 +++++++++
 libgfortran/intrinsics/env.c          | 7 ++-----
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/gcc/testsuite/gfortran.dg/pr96486.f90 b/gcc/testsuite/gfortran.dg/pr96486.f90
new file mode 100644
index 00000000000..fdc7025d61c
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr96486.f90
@@ -0,0 +1,9 @@
+! { dg-do run }
+
+program test
+  implicit none
+  character(0) :: value
+  integer :: l, stat
+  call get_environment_variable("HOME",value,length=l,status=stat)
+  if (stat.ne.-1) stop 1
+end program test
diff --git a/libgfortran/intrinsics/env.c b/libgfortran/intrinsics/env.c
index b7837b30873..7ab0b443897 100644
--- a/libgfortran/intrinsics/env.c
+++ b/libgfortran/intrinsics/env.c
@@ -110,10 +110,7 @@ get_environment_variable_i4 (char *name, char *value, GFC_INTEGER_4 *length,
 
   if (value != NULL)
     { 
-      if (value_len < 1)
-	runtime_error ("Zero-length string passed as value to "
-		       "get_environment_variable.");
-      else
+      if (value_len > 0)
 	memset (value, ' ', value_len); /* Blank the string.  */
     }
 
@@ -138,7 +135,7 @@ get_environment_variable_i4 (char *name, char *value, GFC_INTEGER_4 *length,
 	      memcpy (value, res, value_len);
 	      stat = GFC_VALUE_TOO_SHORT;
 	    }
-	  else
+	  else if (res_len > 0)
 	    memcpy (value, res, res_len);
 	}
     }