Add lowmem flag.lowmem

This disables optimizations in select modules that cause
problems compiling in lower memory environments.

(LaTeX reader, LaTeX and Markdown writers)

Performance is 10x slower for reading LaTeX, 20% slower for
writing Markdown and LaTeX.

1 files changed, 8 insertions, 0 deletions

diff --git a/pandoc.cabal b/pandoc.cabal
index ad325ee24..b588c5714 100644
--- a/pandoc.cabal
+++ b/pandoc.cabal
@@ -392,6 +392,12 @@ flag embed_data_files
   Description:   Embed data files in binary for relocatable executable.
   Default:       False
 
+flag lowmem
+  Description:   Disable optimization on three modules that need a lot
+                 of memory to compile.  Set this flag if your pandoc
+                 build is failing due to out of memory errors.
+  Default:       False
+
 flag trypandoc
   Description:   Build trypandoc cgi executable.
   Default:       False
@@ -505,6 +511,8 @@ library
   if flag(embed_data_files)
      cpp-options:   -DEMBED_DATA_FILES
      other-modules: Text.Pandoc.Data
+  if flag(lowmem)
+     cpp-options:   -DLOWMEM
   hs-source-dirs:  src
 
   exposed-modules: Text.Pandoc,