A PDF with a JPEG image no longer crashes ReleaseSafe and Debug builds: libjpeg and jbig2dec are built without UBSan, as the rest of MuPDF is

libjpeg calls filter-dct.c's source manager through a function pointer;
with -fsanitize=function on the caller and no type hash on the
uninstrumented callee, the call trapped (Illegal instruction in
jpeg_fill_bit_buffer). The Intel SDM vol. 2 crashed pardes on its first
page.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 7 insertions, 1 deletions

diff --git a/mupdf.zig b/mupdf.zig
index a157e850..eeadaa5d 100644
--- a/mupdf.zig
+++ b/mupdf.zig
@@ -98,13 +98,19 @@ pub fn add(b: *std.Build, io: std.Io, dependency: *std.Build.Dependency, options
     module.addCSourceFiles(.{
         .root = dependency.path(""),
         .files = makeSources(b, makelists, "LIBJPEG_SRC"),
-        .flags = &.{"-std=gnu11"},
+        // libjpeg calls back into source/fitz (filter-dct.c's source
+        // manager), which is built without UBSan: -fsanitize=function at
+        // such a call finds no type hash on the callee and traps, so any
+        // PDF with a DCT image crashed ReleaseSafe and Debug builds in
+        // jpeg_fill_bit_buffer. The same holds for jbig2dec below.
+        .flags = &.{ "-std=gnu11", "-fno-sanitize=undefined" },
     });
     module.addCSourceFiles(.{
         .root = dependency.path(""),
         .files = makeSources(b, makelists, "JBIG2DEC_SRC"),
         .flags = &.{
             "-std=gnu11",
+            "-fno-sanitize=undefined",
             "-DHAVE_STDINT_H",
             "-DJBIG_EXTERNAL_MEMENTO_H=\"mupdf/memento.h\"",
         },