BUG: f2py incorrectly translates dimension declarations.

In fortran functions passed to f2py, calculations that occur in the
dimensions of array declarations are interpreted as floats.  Valid
fortran requires integers.  Problem only occurs with fortran functions
not subroutines as only for the former does f2py generate fortran
wrapper code that fails to compile.

Relevant code is in numpy.f2py.crackfortran.getlincoef(), which
calculates and returns the coefficients to getarrlen() for writing to
the fortran wrapper code.

Fixes gh-8062.

2 files changed, 31 insertions, 0 deletions

diff --git a/numpy/f2py/crackfortran.py b/numpy/f2py/crackfortran.py
index 3d2f97a56..2614d3dca 100755
--- a/numpy/f2py/crackfortran.py
+++ b/numpy/f2py/crackfortran.py
@@ -2156,6 +2156,15 @@ def getlincoef(e, xset):  # e = a*x+b ; x in xset
                     m1 = re_1.match(ee)
                 c2 = myeval(ee, {}, {})
                 if (a * 0.5 + b == c and a * 1.5 + b == c2):
+                    # gh-8062: return integers instead of floats if possible.
+                    try:
+                        a = int(a)
+                    except:
+                        pass
+                    try:
+                        b = int(b)
+                    except:
+                        pass
                     return a, b, x
             except Exception:
                 pass
diff --git a/numpy/f2py/tests/test_crackfortran.py b/numpy/f2py/tests/test_crackfortran.py
index 735804024..96adffc72 100644
--- a/numpy/f2py/tests/test_crackfortran.py
+++ b/numpy/f2py/tests/test_crackfortran.py
@@ -86,3 +86,25 @@ class TestPublicPrivate():
         assert 'public' not in mod['vars']['a']['attrspec']
         assert 'private' not in mod['vars']['seta']['attrspec']
         assert 'public' in mod['vars']['seta']['attrspec']
+
+
+class TestArrayDimCalculation(util.F2PyTest):
+    # Issue gh-8062.  Calculations that occur in the dimensions of fortran
+    # array declarations should be interpreted by f2py as integers not floats.
+    # Prior to fix, test fails as generated fortran wrapper does not compile.
+    code = """
+        function test(n, a)
+          integer, intent(in) :: n
+          real(8), intent(out) :: a(0:2*n/2)
+          integer :: test
+          a(:) = n
+          test = 1
+        endfunction
+    """
+
+    def test_issue_8062(self):
+        for n in (5, 11):
+            _, a = self.module.test(n)
+            assert(a.shape == (n+1,))
+            assert_array_equal(a, n)
+