Fixed-function pipeline availability after OpenGL 3.2 core/compatibility split

Answer first

No. GL_CONTEXT_PROFILE_MASK == GL_CONTEXT_PROFILE_COMPATIBILITY alone does not guarantee that every fixed-function entry point is present and usable. A compatibility context is required to expose the legacy pipeline, but the mask only reports the profile you requested, not the completeness of deprecated features on that driver.

Confirmed facts

• OpenGL 3.2 defines core and compatibility profiles. Core removes fixed-function transform, lighting and texture-environment state. Compatibility is required to retain those entry points.
• GL_CONTEXT_PROFILE_MASK reports the profile actually created. A compatibility profile must include all core functionality plus all functionality that was deprecated in 3.2.
• Forward-compatible contexts explicitly remove deprecated functionality. Context creation rules differ between WGL, GLX and EGL.
• GL_ARB_compatibility is not a reliable portable query for legacy support. In practice the compatibility profile itself is the mechanism; the extension is historically tied to the introduction of the split and is not consistently advertised as a runtime extension.

Likely explanation vs spec

The spec mandates the set of legacy features as a whole, not a per-function checklist. Which deprecated extensions are required versus optional is implementation-defined in practice. Most vendors provide the classic fixed-function state, glBegin/glEnd, glTexEnv, fixed-function lighting and matrix stack in compatibility contexts, but support for older imaging or vendor-specific deprecated extensions can vary by driver and platform.

Because the spec does not provide a portable query for "all deprecated functions present", relying on the profile mask alone can lead to undefined behavior on drivers that implement a partial compatibility profile.

Portable steps for this case

1. Create a 3.2+ context with the compatibility flag requested and without the forward-compatible flag.
2. Query GL_CONTEXT_PROFILE_MASK to confirm compatibility, and GL_VERSION to confirm >= 3.2.
3. Do not assume availability. Probe the specific legacy functions you need via function pointers and a runtime test, e.g., call glBegin with a valid mode and check for GL_INVALID_OPERATION.
4. If you need a broader guarantee, test a representative legacy path: matrix mode, glEnable(GL_LIGHTING), glTexEnv. Failure indicates incomplete compatibility on that driver.

One missing diagnostic detail that changes the recommendation: which window system and driver families you must support. WGL, GLX and EGL have different attribute names for profile selection and different historical behavior for compatibility contexts.