Simple readline functionality for interactive python on linux.

Differential Revision: http://reviews.llvm.org/D13268

llvm-svn: 249478

2 files changed, 55 insertions, 6 deletions

diff --git a/lldb/scripts/Python/modules/readline/CMakeLists.txt b/lldb/scripts/Python/modules/readline/CMakeLists.txt
index 11089c6230f..0a4376c1c32 100644
--- a/lldb/scripts/Python/modules/readline/CMakeLists.txt
+++ b/lldb/scripts/Python/modules/readline/CMakeLists.txt
@@ -7,7 +7,11 @@ SET(PYTHON_DIRECTORY python${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR}/site-
 include_directories(${PYTHON_INCLUDE_DIR})
 add_library(readline SHARED readline.cpp)
 
-target_link_libraries(readline ${PYTHON_LIBRARY})
+if (NOT LLDB_DISABLE_LIBEDIT)
+  target_link_libraries(readline ${PYTHON_LIBRARY} edit)
+else()
+  target_link_libraries(readline ${PYTHON_LIBRARY})
+endif()
 
 # FIXME: the LIBRARY_OUTPUT_PATH seems to be ignored - this is not a
 # functional issue for the build dir, though, since the shared lib dir
diff --git a/lldb/scripts/Python/modules/readline/readline.cpp b/lldb/scripts/Python/modules/readline/readline.cpp
index b0d6b748605..38268f8a4b6 100644
--- a/lldb/scripts/Python/modules/readline/readline.cpp
+++ b/lldb/scripts/Python/modules/readline/readline.cpp
@@ -1,23 +1,68 @@
 #include <stdio.h>
 #include "Python.h"
 
-// Python readline module intentionally built to not implement the
-// readline module interface. This is meant to work around llvm
-// pr18841 to avoid seg faults in the stock Python readline.so linked
-// against GNU readline.
+#ifndef LLDB_DISABLE_LIBEDIT
+#include <editline/readline.h>
+#endif
+
+// Simple implementation of the Python readline module using libedit.
+// In the event that libedit is excluded from the build, this turns
+// back into a null implementation that blocks the module from pulling
+// in the GNU readline shared lib, which causes linkage confusion when
+// both readline and libedit's readline compatibility symbols collide.
+//
+// Currently it only installs a PyOS_ReadlineFunctionPointer, without
+// implementing any of the readline module methods. This is meant to
+// work around LLVM pr18841 to avoid seg faults in the stock Python
+// readline.so linked against GNU readline.
 
 static struct PyMethodDef moduleMethods[] =
 {
     {nullptr, nullptr, 0, nullptr}
 };
 
+#ifndef LLDB_DISABLE_LIBEDIT
+PyDoc_STRVAR(
+    moduleDocumentation,
+    "Simple readline module implementation based on libedit.");
+#else
 PyDoc_STRVAR(
     moduleDocumentation,
-    "Stub module meant to effectively disable readline support.");
+    "Stub module meant to avoid linking GNU readline.");
+#endif
+
+#ifndef LLDB_DISABLE_LIBEDIT
+static char*
+simple_readline(FILE *stdin, FILE *stdout, char *prompt)
+{
+    rl_instream = stdin;
+    rl_outstream = stdout;
+    char* line = readline(prompt);
+    if (!line)
+    {
+        char* ret = (char*)PyMem_Malloc(1);
+        if (ret != NULL)
+            *ret = '\0';
+        return ret;
+    }
+    if (*line)
+        add_history(line);
+    int n = strlen(line);
+    char* ret = (char*)PyMem_Malloc(n + 2);
+    strncpy(ret, line, n);
+    free(line);
+    ret[n] = '\n';
+    ret[n+1] = '\0';
+    return ret;
+}
+#endif
 
 PyMODINIT_FUNC
 initreadline(void)
 {
+#ifndef LLDB_DISABLE_LIBEDIT
+    PyOS_ReadlineFunctionPointer = simple_readline;
+#endif
     Py_InitModule4(
         "readline",
         moduleMethods,