Read gl.symbols when generating stubs for libGL.so.

Instead of generating symbols for everything in gl.xml, read the symbol
list from src/GL/gl.symbols and only generate the functions listed
there.

That way, when new functions get added to gl.xml, we won't add any more
symbols in libGL.so.

To do that, if the target parameter to gen_gldispatch_mapi.py is a
filename, then it will read that file for symbols instead of calling
genCommon.getExportNamesFromRoots.

Also added a new genCommon.readSymbolsFile function, which is mostly
copied from symbols-check.py.

src/GLdispatch/vnd-glapi/Makefile.am

@@ -82,8 +82,8 @@ libglapi_gl_la_CPPFLAGS = $(ENTRYPOINT_CPPFLAGS) \
 noinst_HEADERS += g_glapi_mapi_gl_tmp.h
 if HAVE_PYTHON
 BUILT_SOURCES += g_glapi_mapi_gl_tmp.h
-g_glapi_mapi_gl_tmp.h : $(glapi_gen_mapi_deps)
-	$(glapi_gen_mapi) gl $(glapi_gen_gl_xml) > $@
+g_glapi_mapi_gl_tmp.h : $(glapi_gen_mapi_deps) $(top_srcdir)/src/GL/gl.symbols
+	$(glapi_gen_mapi) $(top_srcdir)/src/GL/gl.symbols $(glapi_gen_gl_xml) > $@
 endif
 
 noinst_LTLIBRARIES += libglapi_opengl.la

src/generate/genCommon.py

@@ -34,7 +34,6 @@ MAPI_TABLE_NUM_DYNAMIC = 4096
 
 _LIBRARY_FEATURE_NAMES = {
     # libGL and libGLdiapatch both include every function.
-    "gl" : None,
     "gldispatch" : None,
     "opengl" : frozenset(( "GL_VERSION_1_0", "GL_VERSION_1_1",
         "GL_VERSION_1_2", "GL_VERSION_1_3", "GL_VERSION_1_4", "GL_VERSION_1_5",
@@ -76,6 +75,47 @@ def getFunctionsFromRoots(roots):
 
     return functions
 
+def readSymbolsFile(symbols_file):
+    """
+    Returns the set of function names based on a list of symbols in a text
+    file.
+    """
+    symbols = set()
+    with open(symbols_file) as f:
+        qualifier_optional = '(optional)'
+        for line in f.readlines():
+
+            # Strip comments
+            line = line.split('#')[0]
+            line = line.strip()
+            if not line:
+                continue
+
+            # Line format:
+            # [qualifier] symbol
+            qualifier = None
+            symbol = None
+
+            fields = line.split()
+            if len(fields) == 1:
+                symbol = fields[0]
+            elif len(fields) == 2:
+                qualifier = fields[0]
+                symbol = fields[1]
+            else:
+                raise ValueError(symbols_file + ': invalid format: ' + line)
+
+            # The only supported qualifier is 'optional', which means the
+            # symbol doesn't have to be exported by the library
+            if qualifier and not qualifier == qualifier_optional:
+                raise ValueError(symbols_file + ': invalid qualifier: ' + qualifier)
+
+            # For our purposes here, we expect generated functions to be
+            # mandatory symbols.
+            if qualifier != qualifier_optional:
+                symbols.add(symbol)
+    return symbols
+
 def getExportNamesFromRoots(target, roots):
     """
     Goes through the <feature> tags from gl.xml and returns a set of OpenGL

src/generate/gen_gldispatch_mapi.py

@@ -34,6 +34,7 @@ Generates the glapi_mapi_tmp.h header file from Khronos's XML file.
 
 import sys
 import xml.etree.ElementTree as etree
+import os.path
 
 import genCommon
 
@@ -44,7 +45,15 @@ def _main():
     roots = [ etree.parse(filename).getroot() for filename in xmlFiles ]
     allFunctions = genCommon.getFunctionsFromRoots(roots)
 
-    names = genCommon.getExportNamesFromRoots(target, roots)
+    # Technically, libGL.so is only supposed to export OpenGL 1.2 plus
+    # ARB_multitexture, but in the past, implementations exported everything
+    # and many applications rely on that. Here, we read a list of symbols from
+    # a file instead of exporting everything -- buggy applications won't break,
+    # but libGL.so won't get any *more* symbols added to it.
+    if os.path.isfile(target):
+        names = genCommon.readSymbolsFile(target)
+    else:
+        names = genCommon.getExportNamesFromRoots(target, roots)
     functions = [f for f in allFunctions if(f.name in names)]
 
     if (target in ("gl", "gldispatch")):

src/generate/meson.build

@@ -23,7 +23,6 @@
 
 
 foreach t : [['glapi_mapi_tmp.h', 'gldispatch'],
-             ['g_glapi_mapi_gl_tmp.h', 'gl'],
              ['g_glapi_mapi_opengl_tmp.h', 'opengl'],
              ['g_glapi_mapi_glesv1_tmp.h', 'glesv1'],
              ['g_glapi_mapi_glesv2_tmp.h', 'glesv2']]
@@ -43,6 +42,18 @@ foreach t : [['glapi_mapi_tmp.h', 'gldispatch'],
   set_variable(var, _t)
 endforeach
 
+# For libGL.so, we read the symbol list from a file instead of generating it
+# from the XML files.
+_t = custom_target(
+  'g_glapi_mapi_gl_tmp.h',
+  input : ['gen_gldispatch_mapi.py', '../GL/gl.symbols', 'xml/gl.xml', 'xml/gl_other.xml'],
+  output : 'g_glapi_mapi_gl_tmp.h',
+  command : [prog_py, '@INPUT0@', '@INPUT1@', '@INPUT2@', '@INPUT3@'],
+  depend_files : files('genCommon.py'),
+  capture : true,
+)
+set_variable('g_glapi_mapi_gl_tmp.h'.underscorify(), _t)
+
 foreach target : ['header', 'source']
   ext = target == 'header' ? 'h' : 'c'
   _t = custom_target(