Structured SARIF Diagnostics

The MSVC compiler can be made to output diagnostics as SARIF (Static Analysis Results Interchange Format). SARIF is a machine-readable JSON-based format.

There are two ways to make the MSVC compiler produce SARIF diagnostics:

• Pass the /experimental:log switch on the command line. See the documentation for /experimental:log for details.
• Launch cl.exe programatically and set the SARIF_OUTPUT_PIPE environment variable to retrieve SARIF blocks through a pipe.

Retrieving SARIF through a pipe

Tools that consume SARIF from the MSVC compiler while a compilation is in progress use a pipe. See the documentation for CreatePipe for details about creating Windows pipes.

To retrieve SARIF through a pipe, set the SARIF_OUTPUT_PIPE environment variable to be the UTF-16-encoded integer representation of the HANDLE to the write end of the pipe, then launch cl.exe. SARIF is sent along the pipe as follows:

• When a new diagnostic is available, it is written to this pipe.
• Diagnostics are written to the pipe one-at-a-time rather than as an entire SARIF object.
• Each diagnostic is represented by a JSON-RPC 2.0 message of type Notification.
• The JSON-RPC message is prefixed with a Content-Length header with the form Content-Length: <N> followed by two newlines, where <N> is the length of the following JSON-RPC message in bytes.
• The JSON-RPC message and header are both encoded in UTF-8.
• This JSON-RPC-with-header format is compatible with vs-streamjsonrpc.
• The method name for the JSON-RPC call is OnSarifResult.
• The call has a single parameter that is encoded by-name with the parameter name result.
• The value of the argument is a single result object as specified by the SARIF Version 2.1 standard.

Example

Here's an example of a JSON-RPC SARIF result produced by cl.exe:

Content-Length: 334

{"jsonrpc":"2.0","method":"OnSarifResult","params":{"result":{"ruleId":"C1034","level":"fatal","message":{"text":"iostream: no include path set"},"locations":[{"physicalLocation":{"artifactLocation":{"uri":"file:///C:/Users/sybrand/source/repos/cppcon-diag/cppcon-diag/cppcon-diag.cpp"},"region":{"startLine":1,"startColumn":10}}}]}}}{"jsonrpc":"2.0","method":"OnSarifResult","params":{"result":{"ruleId":"C1034","level":"fatal","message":{"text":"iostream: no include path set"},"locations":[{"physicalLocation":{"artifactLocation":{"uri":"file:///C:/Users/sybrand/source/repos/cppcon-diag/cppcon-diag/cppcon-diag.cpp"},"region":{"startLine":1,"startColumn":10}}}]}}}

SARIF result data

The compiler outputs SARIF that may include additional information to represent the nested structure of some diagnostics. A diagnostic (represented by a result SARIF object) may contain a "diagnostic tree" of additional information in its relatedLocations field. This tree is encoded using a SARIF property bag as follows:

A location object's properties field may contain a nestingLevel property whose value is the depth of this location in the diagnostic tree. If a location doesn't have a nestingLevel specified, the depth is considered to be 0 and this location is a child of the root diagnostic represented by the result object containing it. Otherwise, if the value is greater than the depth of the location immediately preceding this location in the relatedLocations field, this location is a child of that location. Otherwise, this location is a sibling of the closest preceding location in the relatedLocations field with the same depth.

Example

Consider the following code:

struct dog {};
struct cat {};

void pet(dog);
void pet(cat);

struct lizard {};

int main() {
    pet(lizard{});
}

When this code is compiled, the compiler produces the following result object (physicalLocation properties have been removed for brevity):

{
    "ruleId": "C2665",
    "level": "error",
    "message": {
        "text": "'pet': no overloaded function could convert all the argument types"
    },
    "relatedLocations": [
        {
            "id": 0,
            "message": {
                "text": "could be 'void pet(cat)'"
            }
        },
        {
            "id": 1,
            "message": {
                "text": "'void pet(cat)': cannot convert argument 1 from 'lizard' to 'cat'"
            },
            "properties": {
                "nestingLevel": 1
            }
        },
        {
            "id": 2,
            "message": {
                "text": "No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called"
            },
            "properties": {
                "nestingLevel": 2
            }
        },
        {
            "id": 3,
            "message": {
                "text": "or       'void pet(dog)'"
            }
        },
        {
            "id": 4,
            "message": {
                "text": "'void pet(dog)': cannot convert argument 1 from 'lizard' to 'dog'"
            },
            "properties": {
                "nestingLevel": 1
            }
        },
        {
            "id": 5,
            "message": {
                "text": "No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called"
            },
            "properties": {
                "nestingLevel": 2
            }
        },
        {
            "id": 6,
            "message": {
                "text": "while trying to match the argument list '(lizard)'"
            }
        }
    ]
}

The logical diagnostics tree produced from the messages in this result object is:

• 'pet': no overloaded function could convert all the argument types
  • could be 'void pet(cat)'
    • 'void pet(cat)': cannot convert argument 1 from 'lizard' to 'cat
      • No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
  • or 'void pet(dog)'
    • 'void pet(dog)': cannot convert argument 1 from 'lizard' to 'dog'
      • No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
  • while trying to match the argument list '(lizard)'

See also

/experimental:log (Enable structured SARIF diagnostics)