Fix #305: Fix PDF export from matplotlib

Makefile

@@ -29,7 +29,7 @@ LDFLAGS=\
   -s EMULATE_FUNCTION_POINTER_CASTS=1 \
   -s LINKABLE=1 \
   -s EXPORT_ALL=1 \
-	-s EXPORTED_FUNCTIONS='["___cxa_guard_acquire"]' \
+	-s EXPORTED_FUNCTIONS='["___cxa_guard_acquire", "__ZNSt3__28ios_base4initEPv"]' \
   -s WASM=1 \
 	-s SWAPPABLE_ASM_MODULE=1 \
 	-s USE_FREETYPE=1 \

test/test_matplotlib.py

@@ -16,3 +16,15 @@ def test_svg(selenium):
     content = selenium.run("fd.getvalue().decode('utf8')")
     assert len(content) == 15752
     assert content.startswith("<?xml")
+
+
+def test_pdf(selenium):
+    selenium.load_package("matplotlib")
+    selenium.run("from matplotlib import pyplot as plt")
+    selenium.run("plt.figure()")
+    selenium.run("x = plt.plot([1,2,3])")
+    selenium.run("import io")
+    selenium.run("fd = io.BytesIO()")
+    selenium.run("plt.savefig(fd, format='svg')")
+    content = selenium.run("fd.getvalue()")
+    assert len(content) == 15752