Customize log filename via pattern tokens in ZEL_LOADER_LOG_FILE - #499

source/utils/ze_logger.cpp:134

• expandLogFilePattern() computes PID, process name (/proc/self/exe readlink), and timestamp even when the filename contains no '%' tokens (e.g., the default "ze_loader.log"). This adds avoidable overhead and extra syscalls during logger creation. Add a fast-path to return the pattern unchanged when it contains no '%' at all.

std::string expandLogFilePattern(const std::string &pattern) {
    if (pattern.empty()) {
        return pattern;
    }

source/utils/ze_logger.cpp:146

• createLogger() and comments mention supporting a literal percent token ("%%"), but expandLogFilePattern() currently treats "%%" as two characters (it doesn't collapse to a single '%'). If you intend to support "%%" as an escape for a literal percent, handle it explicitly in the token switch.

    for (std::size_t i = 0; i < pattern.size(); ++i) {
        if (pattern[i] == '%' && i + 1 < pattern.size()) {
            switch (pattern[i + 1]) {
                case 'P':
                    expanded += pid;

test/ze_logger_filename_pattern_unit_tests.cpp:81

• Test name uses "ThenReturned..." while the rest of this file consistently uses "ThenReturns...". Renaming improves consistency and makes searches/filters more predictable.

TEST(ZeLoggerExpandLogFilePattern, GivenNoTokenThenReturnedUnchanged) {

source/utils/ze_logger.cpp:149

• expandLogFilePattern() recomputes pid/process name/timestamp on every call and reserves capacity without accounting for the timestamp, which adds avoidable syscalls/allocations and can make %T vary across multiple expansions within the same process. Cache these values once per process and include timestamp.size() in the reserve calculation.

    const std::string pid = std::to_string(static_cast<long long>(GET_PID()));
    const std::string process_name = currentProcessName();
    const std::string timestamp = startupTimestampForFileName();

    std::string expanded;

test/ze_logger_filename_pattern_unit_tests.cpp:63

• Test name uses "ThenReturned..." while the rest of this file consistently uses "ThenReturns...". Renaming improves consistency and makes searches/filters more predictable.

This issue also appears on line 81 of the same file.

TEST(ZeLoggerSanitizeFileNameComponent, GivenPlainNameThenReturnedUnchanged) {

source/utils/ze_logger.cpp:14

• <cctype> is included but not used anywhere in this file; it can be removed to avoid unnecessary headers and potential lint warnings.

#include <cerrno>
#include <cctype>
#include <chrono>

source/utils/ze_logger.cpp:694

• expandLogFilePattern() can trigger readlink()/time/getpid() when ZEL_LOADER_LOG_FILE contains tokens, but this is executed before checking whether logging is enabled or whether console logging is selected. That adds avoidable syscalls in the !logging_enabled fast path and when ZEL_LOADER_LOG_CONSOLE=1 (file name is unused). Consider only expanding when file logging will actually be used.

    // Expand filename pattern tokens (%P, %N, %T, %%) within ZEL_LOADER_LOG_FILE.
    // A filename without tokens is returned unchanged, preserving existing behaviour.
    std::string resolved_loader_file = expandLogFilePattern(loader_file);
    if (resolved_loader_file.empty()) {
        resolved_loader_file = loader_file;

source/utils/ze_logger.cpp:149

• %P is cached in a function-local static const std::string. After fork(), the child inherits that cached value, so %P can incorrectly expand to the parent PID. Since %P is intended to disambiguate per-process logs, compute the PID per call (or otherwise detect PID changes) instead of caching it permanently.

This issue also appears on line 690 of the same file.

    // The token values are process-invariant, so compute them once (thread-safe
    // function-local statics) rather than issuing the pid/exe-path/time syscalls
    // on every call. Caching also gives %T a stable "logger startup" timestamp
    // across expansions instead of drifting between calls.
    static const std::string pid = std::to_string(static_cast<long long>(GET_PID()));
    static const std::string process_name = currentProcessName();
    static const std::string timestamp = startupTimestampForFileName();