render: Fix cells spanning otherwise completely empty rows/columns.

When adjacent rows or columns contain only spanned cells and no rules give
the rows or columns a natural minimum height or width, this triggers a
special case in distribute_spanned_width().  This special case had not been
tested and (therefore) was broken.  This commit fixes the problem and adds
test cases to prevent it from recurring.

Bug #31346.

diff --git a/src/output/render.c b/src/output/render.c
index 094e68799cf93b7e72be846075f8e04da80ec499..6722a13dc2e1100a99fc0f3d8b971a14150e665e 100644 (file)
--- a/src/output/render.c
+++ b/src/output/render.c
@@ -359,9 +359,14 @@ distribute_spanned_width (int width,
      w1 by the common denominator of all three calculations (d), dividing that
      out in the column width calculation, and then keeping the remainder for
      the next iteration.
+
+     (We actually compute the unspanned width of a column as twice the
+     unspanned width, plus the width of the rule on the left, plus the width of
+     the rule on the right.  That way each rule contributes to both the cell on
+     its left and on its right.)
   */
   d0 = n;
-  d1 = total_unspanned * 2.0;
+  d1 = 2.0 * (total_unspanned > 0 ? total_unspanned : 1.0);
   d = d0 * d1;
   if (total_unspanned > 0)
     d *= 2.0;

diff --git a/tests/output/render.at b/tests/output/render.at
index 902a5b6be6072bf1b0cd9f3de6d4c3162465acb9..a39f688d68af2103ac124563564d9e2f1df4c395 100644 (file)
--- a/tests/output/render.at
+++ b/tests/output/render.at
@@ -292,6 +292,36 @@ AT_CHECK([render-test input], [0], [dnl
 ])
 AT_CLEANUP
 
+dnl This checks for bug #31346, a segmentation fault that surfaced
+dnl when two or more rows  had no unspanned cells and no rules.
+AT_SETUP([joined rows only, no rules])
+AT_KEYWORDS([render rendering])
+AT_DATA([input], [2 2
+2*1 ab\ncd\nef
+2*1 hij\nklm\nnop
+])
+AT_CHECK([render-test input], [0], [dnl
+abhij
+cdklm
+efnop
+])
+AT_CLEANUP
+
+AT_SETUP([joined columns only, no rules])
+AT_KEYWORDS([render rendering])
+AT_DATA([input], [2 2
+1*2 abc\ndef
+1*2 hij\nklm\nnop
+])
+AT_CHECK([render-test input], [0], [dnl
+abc
+def
+hij
+klm
+nop
+])
+AT_CLEANUP
+
 AT_SETUP([5 big narrow cells])
 AT_KEYWORDS([render rendering])
 AT_DATA([input], [1 5