fix: apply suggestions from code review

---
type: pre_commit_static_analysis_report
description: Results of running static analysis checks when committing changes.
report:
  - task: lint_filenames
    status: passed
  - task: lint_editorconfig
    status: passed
  - task: lint_markdown
    status: na
  - task: lint_package_json
    status: na
  - task: lint_repl_help
    status: na
  - task: lint_javascript_src
    status: na
  - task: lint_javascript_cli
    status: na
  - task: lint_javascript_examples
    status: na
  - task: lint_javascript_tests
    status: passed
  - task: lint_javascript_benchmarks
    status: na
  - task: lint_python
    status: na
  - task: lint_r
    status: na
  - task: lint_c_src
    status: missing_dependencies
  - task: lint_c_examples
    status: na
  - task: lint_c_benchmarks
    status: na
  - task: lint_c_tests_fixtures
    status: na
  - task: lint_shell
    status: na
  - task: lint_typescript_declarations
    status: passed
  - task: lint_typescript_tests
    status: na
  - task: lint_license_headers
    status: passed
---

Author: headlessNode

lib/node_modules/@stdlib/blas/ext/base/ddiff/binding.gyp

@@ -29,6 +29,39 @@
     # Target name should match the add-on export name:
     'addon_target_name%': 'addon',
 
+    # Fortran compiler (to override -Dfortran_compiler=<compiler>):
+    'fortran_compiler%': 'gfortran',
+
+    # Fortran compiler flags:
+    'fflags': [
+      # Specify the Fortran standard to which a program is expected to conform:
+      '-std=f95',
+
+      # Indicate that the layout is free-form source code:
+      '-ffree-form',
+
+      # Aggressive optimization:
+      '-O3',
+
+      # Enable commonly used warning options:
+      '-Wall',
+
+      # Warn if source code contains problematic language features:
+      '-Wextra',
+
+      # Warn if a procedure is called without an explicit interface:
+      '-Wimplicit-interface',
+
+      # Do not transform names of entities specified in Fortran source files by appending underscores (i.e., don't mangle names, thus allowing easier usage in C wrappers):
+      '-fno-underscoring',
+
+      # Warn if source code contains Fortran 95 extensions and C-language constructs:
+      '-pedantic',
+
+      # Compile but do not link (output is an object file):
+      '-c',
+    ],
+
     # Set variables based on the host OS:
     'conditions': [
       [
@@ -128,6 +161,68 @@
           },
         ], # end condition (OS!="win")
       ], # end conditions
+
+      # Define custom build actions for particular inputs:
+      'rules': [
+        {
+          # Define a rule for processing Fortran files:
+          'extension': 'f',
+
+          # Define the pathnames to be used as inputs when performing processing:
+          'inputs': [
+            # Full path of the current input:
+            '<(RULE_INPUT_PATH)'
+          ],
+
+          # Define the outputs produced during processing:
+          'outputs': [
+            # Store an output object file in a directory for placing intermediate results (only accessible within a single target):
+            '<(INTERMEDIATE_DIR)/<(RULE_INPUT_ROOT).<(obj)'
+          ],
+
+          # Define the rule for compiling Fortran based on the host OS:
+          'conditions': [
+            [
+              'OS=="win"',
+
+              # Rule to compile Fortran on Windows:
+              {
+                'rule_name': 'compile_fortran_windows',
+                'message': 'Compiling Fortran file <(RULE_INPUT_PATH) on Windows...',
+
+                'process_outputs_as_sources': 0,
+
+                # Define the command-line invocation:
+                'action': [
+                  '<(fortran_compiler)',
+                  '<@(fflags)',
+                  '<@(_inputs)',
+                  '-o',
+                  '<@(_outputs)',
+                ],
+              },
+
+              # Rule to compile Fortran on non-Windows:
+              {
+                'rule_name': 'compile_fortran_linux',
+                'message': 'Compiling Fortran file <(RULE_INPUT_PATH) on Linux...',
+
+                'process_outputs_as_sources': 1,
+
+                # Define the command-line invocation:
+                'action': [
+                  '<(fortran_compiler)',
+                  '<@(fflags)',
+                  '-fPIC', # generate platform-independent code
+                  '<@(_inputs)',
+                  '-o',
+                  '<@(_outputs)',
+                ],
+              }
+            ], # end condition (OS=="win")
+          ], # end conditions
+        }, # end rule (extension=="f")
+      ], # end rules
     }, # end target <(addon_target_name)
 
     # Target to copy a generated add-on to a standard location:

lib/node_modules/@stdlib/blas/ext/base/ddiff/src/main.c

@@ -123,8 +123,10 @@ static void stdlib_strided_base_ddiff_ndarray( const CBLAS_INT N, const double *
 		}
 	} else if ( N > 0 ) {
 		prev = X[ offsetX ];
+		io = offsetX;
 	} else {
 		prev = append[ offsetA ];
+		io = offsetA;
 	}
 
 	// x
@@ -216,7 +218,7 @@ void API_SUFFIX(stdlib_strided_ddiff_ndarray)( const CBLAS_INT N, const CBLAS_IN
 
 		// Copy `append` into output array:
 		io = offsetOut + ( ( N1 + N ) * strideOut );
-		c_dcopy_ndarray( N, append, strideA, offsetA, out, strideOut, io );
+		c_dcopy_ndarray( N2, append, strideA, offsetA, out, strideOut, io );
 	}
 
 	if ( k == 1 ) {

lib/node_modules/@stdlib/blas/ext/base/ddiff/test/test.ndarray.native.js

@@ -135,6 +135,9 @@ tape( 'the function calculates the k-th discrete forward differences of a double
 	t.deepEqual( o, expected, 'returns expected value' );
 	t.strictEqual( out, o, 'return expected value' );
 
+	o = new Float64Array( 4 );
+	w = new Float64Array( 4 );
+
 	out = ddiff( x.length, 1, x, 1, 0, 0, p, 1, 0, 0, a, 1, 0, o, 1, 0, w, 1, 0 ); // eslint-disable-line max-len
 	expected = new Float64Array([
 		4.0,