Copilot Global Variable Analysis #37
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Global Variables Used Together - Code ExamplesThis document provides concrete examples of global variables that are frequently used together in the libtrn codebase. Example 1: Newsgroup Navigation (ng.cpp)// These variables are used together to manage newsgroup state
set_data_source(g_newsgroup_ptr->rc->data_source); // Line 140
if (change_dir(g_data_source->spool_dir)) // Line 142
{
std::printf(g_no_cd, g_data_source->spool_dir); // Line 144
return NG_ERROR;
}Variables used together:
Coupling: These two variables must be kept in sync. When Example 2: Article and Threading StateFrom the analysis, these variables frequently appear together: // Pseudocode showing typical usage pattern
if (g_threaded_group) {
// Navigate through g_first_subject, g_last_subject
for (Subject *sp = g_first_subject; sp; sp = sp->next) {
// Process articles in thread
}
}
// Article navigation uses multiple globals
for (ArticleNum an = g_abs_first; an <= g_last_art; an++) {
Article *ap = g_artp;
// Process article
}Variables used together:
Example 3: Selection Mode StateVariables from the selection system that work together:
These form a cohesive group managing the selection UI state. Example 4: Display ManagementVariables that control screen rendering:
Example 5: Article Buffer ManagementThese variables form a cluster for article content handling:
All appear together ~98 times across files, indicating tight coupling. Example 6: Caching InfrastructureVariables that manage article caching: // Typical caching logic pattern
if (g_cached_all_in_range) {
// Use g_first_cached and g_last_cached to define range
for (ArticleNum an = g_first_cached; an <= g_last_cached; an++) {
// Access cached article
}
}Variables:
These 3 variables appear together in 10+ files. Example 7: Mode and Command State// Mode management - these globals track application state
switch (g_mode) {
case MM_NEWSGROUP:
// Use g_newsgroup_ptr, g_in_ng
break;
case MM_ARTICLE:
// Use g_art, g_artp
break;
}
// General mode affects behavior across the application
if (g_general_mode & GM_SPECIAL) {
// Special handling with g_default_cmd
}Variables:
Common PatternsPattern 1: Paired List ManagementVariables that come in pairs for managing lists:
Pattern 2: Current + CollectionA "current" pointer with its collection:
Pattern 3: UI State ClustersSelection system:
Pattern 4: Context-Dependent GroupsNewsgroup context requires:
Statistics Summary
Refactoring OpportunitiesBased on the usage patterns, these variable groups are strong candidates for encapsulation:
ConclusionThe analysis reveals strong coupling between many global variables in libtrn. Variables consistently used together should be refactored into cohesive data structures to:
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Global Variables Analysis for libtrn
Summary
The libtrn project in the TRN (Threaded Read News) codebase contains 403 global variables that follow a
g_naming convention. This analysis identifies which global variables are frequently used together, indicating potential coupling and dependencies.Methodology
libtrndirectoryexterndeclarations in header filesTop 30 Most Connected Global Variables
These variables appear together with many other globals across multiple files, indicating they are central to the application state:
g_data_sourceg_general_modeg_artg_header_typeg_artpg_abs_firstg_int_countg_curr_artpg_erase_screeng_erase_each_lineg_first_artg_dm_countg_in_ngg_first_subjectg_art_posg_default_cmdg_force_lastg_auto_view_inlineg_charsetsg_do_check_wheng_g_lineg_char_substg_do_hidingg_art_line_numg_cached_all_in_rangeg_first_cachedg_art_buf_leng_first_viewg_art_buf_seekg_art_sizeTop Global Variable Pairs (Most Frequently Used Together)
These pairs of variables are used together across many source files, indicating strong coupling:
Newsgroup Management Cluster (20+ files)
g_current_newsgroup+g_newsgroup_ptr(24 files)g_current_newsgroup+g_data_source(24 files)g_current_newsgroup+g_header_type(21 files)g_data_source+g_newsgroup_ptr(21 files)These variables work together to manage the current newsgroup state.
Article Management Cluster (15+ files)
g_art+g_artp(17 files)g_abs_first+g_first_art(16 files)g_art+g_header_type(16 files)g_artp+g_curr_artp(15 files)These handle current article state and navigation.
Display Management Cluster (10+ files)
g_erase_each_line+g_erase_screen(13 files)g_data_source+g_erase_screen(13 files)g_erase_each_line+g_header_type(12 files)Screen rendering and display management.
Caching Cluster (8+ files)
g_abs_first+g_first_cached(10 files)g_cached_all_in_range+g_first_cached(10 files)g_abs_first+g_last_cached(9 files)Article caching infrastructure.
Variable Groups by Functional Domain
Newsgroup State
g_newsgroup_ptr- Used with 42 other variablesg_current_newsgroupg_first_newsgroupg_last_newsgroupg_recent_newsgroupg_newsgroup_nameg_newsgroup_dirg_newsgroup_to_readSelection System
g_sel_mode- Used with 41 other variablesg_sel_itemsg_sel_rereadingg_sel_maskg_sel_directiong_selected_countg_sel_exclusiveg_sel_item_indexArticle Management
g_art- Current articleg_artp- Article pointerg_curr_artp- Current article pointerg_abs_first- Absolute first articleg_first_art- First articleg_last_art- Last articleg_art_ptr_list+g_art_ptr_list_size- Article pointer listThreading
g_threaded_group- Frequently paired with article variablesg_use_threadsg_first_subjectg_last_subjectDisplay & UI
g_verbose- Used with 38 other variablesg_term_lineg_term_colg_page_lineg_erase_screeng_erase_each_lineg_mouse_bar_cntMode & State
g_mode- Current trn stateg_general_modeg_default_cmdg_in_ng- In newsgroup flagg_waitingUniversal Selector
g_first_univg_last_univg_sel_next_univg_univ_fnameg_univ_titleg_univ_ng_virt_flagg_univ_followRecommendations
High Coupling: Variables like
g_data_source,g_general_mode, andg_newsgroup_ptrare used with 40+ other globals, suggesting they are central state managers that might benefit from encapsulation into state objects.Related Clusters: Consider grouping related variables into structs or classes:
NewsgroupStateclassSelectionManagerclassArticleManagerclassDisplayContextclassPaired Variables: Variables that consistently appear together (like
g_art_ptr_listandg_art_ptr_list_size) should be encapsulated together to prevent inconsistencies.Refactoring Priority: Focus refactoring efforts on the top 30 most connected variables first, as they have the most dependencies and highest maintenance risk.
Files Analyzed
Total files processed: 64 C++ source files in
libtrn/Total global variables found: 403
Analysis date: 10-Nov-2025
Notes
g_prefix makes globals easy to identify but also highlights the extensive use of global stateBeta Was this translation helpful? Give feedback.
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