From 0cf9fb7e415e41f0f58fb1c7567d484ef6b42964 Mon Sep 17 00:00:00 2001 From: Nic Boet Date: Thu, 1 Oct 2026 23:38:40 -0500 Subject: [PATCH] Initialise is_head, and avoid division by zero in 3-line terminals var_init() allocated the matrix with malloc() but never set is_head, so the draw loop read uninitialised memory for cells no stream had touched yet. In old-style scrolling (-o) is_head is never set at all, so after a resize reused freed memory, random characters were drawn as white heads. Initialise it along with val. length[] used rand() % (LINES - 3), which divides by zero when the terminal is exactly 3 lines tall at start-up (SIGFPE). Clamp the modulus to at least 1. --- cmatrix.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/cmatrix.c b/cmatrix.c index 7d8ca39..ed66de4 100644 --- a/cmatrix.c +++ b/cmatrix.c @@ -223,6 +223,7 @@ void var_init() { for (i = 0; i <= LINES; i++) { for (j = 0; j <= COLS - 1; j += 2) { matrix[i][j].val = -1; + matrix[i][j].is_head = false; } } @@ -231,7 +232,7 @@ void var_init() { spaces[j] = (int) rand() % LINES + 1; /* And length of the stream */ - length[j] = (int) rand() % (LINES - 3) + 3; + length[j] = (int) rand() % (LINES > 3 ? LINES - 3 : 1) + 3; /* Sentinel value for creation of new objects */ matrix[1][j].val = ' '; @@ -698,7 +699,7 @@ if (console) { spaces[j]--; } else if (matrix[0][j].val == -1 && matrix[1][j].val == ' ') { - length[j] = (int) rand() % (LINES - 3) + 3; + length[j] = (int) rand() % (LINES > 3 ? LINES - 3 : 1) + 3; matrix[0][j].val = (int) rand() % randnum + randmin; spaces[j] = (int) rand() % LINES + 1;