From db4544420fdd7f2504bde88a1f68846e8ba870ed Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Mon, 19 Feb 2024 22:41:17 +0100
Subject: [PATCH] VRTDerivedRasterBand: avoid potential initialization order
 fiasco (fixes #2884)

---
 frmts/vrt/vrtdataset.h             |  2 +-
 frmts/vrt/vrtderivedrasterband.cpp | 35 ++++++++++++++++++++----------
 2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/frmts/vrt/vrtdataset.h b/frmts/vrt/vrtdataset.h
index 439f3341f0db..aa6e352b296e 100644
--- a/frmts/vrt/vrtdataset.h
+++ b/frmts/vrt/vrtdataset.h
@@ -909,7 +909,7 @@ class CPL_DLL VRTDerivedRasterBand CPL_NON_FINAL : public VRTSourcedRasterBand
                                    GDALDerivedPixelFuncWithArgs pfnPixelFunc,
                                    const char *pszMetadata);
 
-    static std::pair<PixelFunc, CPLString> *
+    static const std::pair<PixelFunc, std::string> *
     GetPixelFunction(const char *pszFuncNameIn);
 
     void SetPixelFunctionName(const char *pszFuncNameIn);
diff --git a/frmts/vrt/vrtderivedrasterband.cpp b/frmts/vrt/vrtderivedrasterband.cpp
index b69360ef58ad..f264826c4d6a 100644
--- a/frmts/vrt/vrtderivedrasterband.cpp
+++ b/frmts/vrt/vrtderivedrasterband.cpp
@@ -50,10 +50,6 @@ using namespace GDALPy;
 #define GDAL_VRT_ENABLE_PYTHON_DEFAULT "TRUSTED_MODULES"
 #endif
 
-static std::map<CPLString,
-                std::pair<VRTDerivedRasterBand::PixelFunc, CPLString>>
-    osMapPixelFunction;
-
 /* Flags for getting buffers */
 #define PyBUF_WRITABLE 0x0001
 #define PyBUF_FORMAT 0x0004
@@ -231,6 +227,20 @@ void VRTDerivedRasterBand::Cleanup()
 {
 }
 
+/************************************************************************/
+/*                      GetGlobalMapPixelFunction()                     */
+/************************************************************************/
+
+static std::map<std::string,
+                std::pair<VRTDerivedRasterBand::PixelFunc, std::string>> &
+GetGlobalMapPixelFunction()
+{
+    static std::map<std::string,
+                    std::pair<VRTDerivedRasterBand::PixelFunc, std::string>>
+        gosMapPixelFunction;
+    return gosMapPixelFunction;
+}
+
 /************************************************************************/
 /*                           AddPixelFunction()                         */
 /************************************************************************/
@@ -261,7 +271,7 @@ CPLErr CPL_STDCALL GDALAddDerivedBandPixelFunc(
         return CE_None;
     }
 
-    osMapPixelFunction[pszName] = {
+    GetGlobalMapPixelFunction()[pszName] = {
         [pfnNewFunction](void **papoSources, int nSources, void *pData,
                          int nBufXSize, int nBufYSize, GDALDataType eSrcType,
                          GDALDataType eBufType, int nPixelSpace, int nLineSpace,
@@ -299,13 +309,13 @@ CPLErr CPL_STDCALL GDALAddDerivedBandPixelFuncWithArgs(
     const char *pszName, GDALDerivedPixelFuncWithArgs pfnNewFunction,
     const char *pszMetadata)
 {
-    if (pszName == nullptr || pszName[0] == '\0' || pfnNewFunction == nullptr)
+    if (!pszName || pszName[0] == '\0' || !pfnNewFunction)
     {
         return CE_None;
     }
 
-    osMapPixelFunction[pszName] = {pfnNewFunction,
-                                   pszMetadata != nullptr ? pszMetadata : ""};
+    GetGlobalMapPixelFunction()[pszName] = {pfnNewFunction,
+                                            pszMetadata ? pszMetadata : ""};
 
     return CE_None;
 }
@@ -353,7 +363,7 @@ CPLErr VRTDerivedRasterBand::AddPixelFunction(
  * @return A derived band pixel function, or NULL if none have been
  * registered for pszFuncName.
  */
-std::pair<VRTDerivedRasterBand::PixelFunc, CPLString> *
+const std::pair<VRTDerivedRasterBand::PixelFunc, std::string> *
 VRTDerivedRasterBand::GetPixelFunction(const char *pszFuncNameIn)
 {
     if (pszFuncNameIn == nullptr || pszFuncNameIn[0] == '\0')
@@ -361,9 +371,10 @@ VRTDerivedRasterBand::GetPixelFunction(const char *pszFuncNameIn)
         return nullptr;
     }
 
-    auto oIter = osMapPixelFunction.find(pszFuncNameIn);
+    const auto &oMapPixelFunction = GetGlobalMapPixelFunction();
+    const auto oIter = oMapPixelFunction.find(pszFuncNameIn);
 
-    if (oIter == osMapPixelFunction.end())
+    if (oIter == oMapPixelFunction.end())
         return nullptr;
 
     return &(oIter->second);
@@ -945,7 +956,7 @@ CPLErr VRTDerivedRasterBand::IRasterIO(
     }
 
     /* ---- Get pixel function for band ---- */
-    std::pair<PixelFunc, CPLString> *poPixelFunc = nullptr;
+    const std::pair<PixelFunc, std::string> *poPixelFunc = nullptr;
     std::vector<std::pair<CPLString, CPLString>> oAdditionalArgs;
 
     if (EQUAL(m_poPrivate->m_osLanguage, "C"))