[gnumeric] Style: use heap, not stack, allocation.

[Morten Welinder <mortenw src gnome org>]

commit 537a206a1e263c7225481f95bf0fd8e24c0951c9
Author: Morten Welinder <terra gnome org>
Date:   Thu Nov 30 11:45:15 2017 -0500

    Style: use heap, not stack, allocation.
    
    An allocation of 4*rows pointers is a bit big for the stack if we have
    16k rows.

 ChangeLog         |    5 +++++
 src/sheet-style.c |   20 +++++++++++---------
 2 files changed, 16 insertions(+), 9 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 8d85b7f..ab33923 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-11-30  Morten Welinder  <terra gnome org>
+
+       * src/sheet-style.c (sheet_style_find_conflicts): Use heap, not
+       stack, allocation.
+
 2017-11-29  Morten Welinder  <terra gnome org>
 
        * src/sstest.c (enumerate_functions): Make sure function is loaded.
diff --git a/src/sheet-style.c b/src/sheet-style.c
index d04727b..3f40ee9 100644
--- a/src/sheet-style.c
+++ b/src/sheet-style.c
@@ -2004,6 +2004,7 @@ sheet_style_find_conflicts (Sheet const *sheet, GnmRange const *r,
 {
        int n, col, row, start_col, end_col;
        GnmStyleRow sr;
+       gpointer *sr_array_data;
        GnmStyleBorderLocation i;
        gboolean known[GNM_STYLE_BORDER_EDGE_MAX];
        GnmBorder const *none = gnm_style_border_none ();
@@ -2050,15 +2051,15 @@ sheet_style_find_conflicts (Sheet const *sheet, GnmRange const *r,
 
        /* allocate then alias the arrays for easy access */
        n = end_col - start_col + 2;
-       sr.vertical      = (GnmBorder const **)g_alloca (n *
-                           (3 * sizeof (GnmBorder const *) +
-                            sizeof (GnmStyle const *)));
-       sr.top        = sr.vertical + n;
-       sr.bottom     = sr.top + n;
-       sr.styles     = ((GnmStyle const **) (sr.bottom + n));
-       sr.vertical  -= start_col; sr.top     -= start_col;
-       sr.bottom    -= start_col; sr.styles  -= start_col;
-       sr.start_col  = start_col; sr.end_col  = end_col;
+       g_assert (sizeof (GnmBorder *) == sizeof (gpointer));
+       g_assert (sizeof (GnmStyle *) == sizeof (gpointer));
+       sr_array_data = g_new (gpointer, n * 4);
+       sr.vertical = (GnmBorder const **)(sr_array_data - start_col);
+       sr.top      = (GnmBorder const **)(sr_array_data + n - start_col);
+       sr.bottom   = (GnmBorder const **)(sr_array_data + 2 * n - start_col);
+       sr.styles   = (GnmStyle const **) (sr_array_data + 3 * n - start_col);
+       sr.start_col  = start_col;
+       sr.end_col  = end_col;
        sr.hide_grid  = sheet->hide_grid;
 
        /* pretend the previous bottom had no borders */
@@ -2109,6 +2110,7 @@ sheet_style_find_conflicts (Sheet const *sheet, GnmRange const *r,
        border_mask_vec (known, borders, sr.top, r->start.col, r->end.col,
                         GNM_STYLE_BORDER_BOTTOM);
 
+       g_free (sr_array_data);
        return user.conflicts;
 }