RDKEMW-12350: Fix uninitialized missing error checks in timeZoneDST fallback path

[yogeswaransky]

• Fix zone NULL/uninitialized issues in timezone fallback reader

• Validate ftell return: reject -1 (error) and 0 (empty file)
• Add malloc NULL check to prevent NULL pointer dereference
• Initialize zone buffer to empty string before fscanf
• Reset zone after each iteration to catch stale data
• Check fscanf return == 1 instead of != EOF to catch format errors and whitespace-only files
• Remove impossible 'zone != NULL' check (zone is stack-local pointer to heap memory, never NULL inside the loop)
• Don't reset zoneValue to NULL on empty reads (preserve any previously read valid value)

[Copilot]

Pull request overview

This PR hardens the /opt/persistent/timeZoneDST fallback path in getTimezone() to prevent use of uninitialized data and to add missing error/edge-case handling when reading the timezone file, plus adds unit tests covering the new fallback behavior.

Changes:

• Add ftell() error/empty/oversize checks and malloc() NULL handling in the timeZoneDST fallback reader.
• Tighten parsing to fscanf(...) == 1, initialize the zone buffer, and only update zoneValue on non-empty reads.
• Add gtest coverage for timeZoneDST fallback scenarios (open failure, ftell error, empty, too large, valid timezone).

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

File	Description
source/xconf-client/xconfclient.c	Adds defensive size/alloc validation and safer scanning logic for the timeZoneDST fallback.
source/test/xconf-client/xconfclientTest.cpp	Adds tests that drive appendRequestParams() through the getTimezone() timeZoneDST fallback path.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 7 comments.