gh-101135: Add backwards compatibility to Windows launcher for older 32-bit versions (GH-101138)

Python 2.x and up to 3.4 did not contain the "-32" in their registry name, so the 32 and 64-bit installs were treated equal. Since 3.5/PEP 514 this is no longer true, but we still want to detect the EOL versions correctly in case people are still using them.

Additionally, the code to replace a node with one with a lower sort key was buggy (wrong node chosen, replace never happened since parent was always NULL, replaced node never freed, etc)

Misc/NEWS.d/next/Windows/2023-01-18-18-25-18.gh-issue-101135.HF9VlG.rst

@@ -0,0 +1,3 @@
+Restore ability to launch older 32-bit versions from the :file:`py.exe`
+launcher when both 32-bit and 64-bit installs of the same version are
+available.

PC/launcher2.c

@@ -1294,34 +1294,34 @@ _compareTag(const wchar_t *x, const wchar_t *y)
 
 
 int
-addEnvironmentInfo(EnvironmentInfo **root, EnvironmentInfo *node)
+addEnvironmentInfo(EnvironmentInfo **root, EnvironmentInfo* parent, EnvironmentInfo *node)
 {
     EnvironmentInfo *r = *root;
     if (!r) {
         *root = node;
-        node->parent = NULL;
+        node->parent = parent;
         return 0;
     }
     // Sort by company name
     switch (_compareCompany(node->company, r->company)) {
     case -1:
-        return addEnvironmentInfo(&r->prev, node);
+        return addEnvironmentInfo(&r->prev, r, node);
     case 1:
-        return addEnvironmentInfo(&r->next, node);
+        return addEnvironmentInfo(&r->next, r, node);
     case 0:
         break;
     }
     // Then by tag (descending)
     switch (_compareTag(node->tag, r->tag)) {
     case -1:
-        return addEnvironmentInfo(&r->next, node);
+        return addEnvironmentInfo(&r->next, r, node);
     case 1:
-        return addEnvironmentInfo(&r->prev, node);
+        return addEnvironmentInfo(&r->prev, r, node);
     case 0:
         break;
     }
     // Then keep the one with the lowest internal sort key
-    if (r->internalSortKey < node->internalSortKey) {
+    if (node->internalSortKey < r->internalSortKey) {
         // Replace the current node
         node->parent = r->parent;
         if (node->parent) {
@@ -1334,9 +1334,16 @@ addEnvironmentInfo(EnvironmentInfo **root, EnvironmentInfo *node)
                 freeEnvironmentInfo(node);
                 return RC_INTERNAL_ERROR;
             }
+        } else {
+            // If node has no parent, then it is the root.
+            *root = node;
         }
+
         node->next = r->next;
         node->prev = r->prev;
+
+        debug(L"# replaced %s/%s/%i in tree\n", node->company, node->tag, node->internalSortKey);
+        freeEnvironmentInfo(r);
     } else {
         debug(L"# not adding %s/%s/%i to tree\n", node->company, node->tag, node->internalSortKey);
         return RC_DUPLICATE_ITEM;
@@ -1392,6 +1399,100 @@ _combineWithInstallDir(const wchar_t **dest, const wchar_t *installDir, const wc
 }
 
 
+bool
+_isLegacyVersion(EnvironmentInfo *env)
+{
+    // Check if backwards-compatibility is required.
+    // Specifically PythonCore versions 2.X and 3.0 - 3.5 do not implement PEP 514.
+    if (0 != _compare(env->company, -1, L"PythonCore", -1)) {
+        return false;
+    }
+
+    int versionMajor, versionMinor;
+    int n = swscanf_s(env->tag, L"%d.%d", &versionMajor, &versionMinor);
+    if (n != 2) {
+        debug(L"# %s/%s has an invalid version tag\n", env->company, env->tag);
+        return false;
+    }
+
+    return versionMajor == 2
+        || (versionMajor == 3 && versionMinor >= 0 && versionMinor <= 5);
+}
+
+int
+_registryReadLegacyEnvironment(const SearchInfo *search, HKEY root, EnvironmentInfo *env, const wchar_t *fallbackArch)
+{
+    // Backwards-compatibility for PythonCore versions which do not implement PEP 514.
+    int exitCode = _combineWithInstallDir(
+        &env->executablePath,
+        env->installDir,
+        search->executable,
+        search->executableLength
+    );
+    if (exitCode) {
+        return exitCode;
+    }
+
+    if (search->windowed) {
+        exitCode = _registryReadString(&env->executableArgs, root, L"InstallPath", L"WindowedExecutableArguments");
+    }
+    else {
+        exitCode = _registryReadString(&env->executableArgs, root, L"InstallPath", L"ExecutableArguments");
+    }
+    if (exitCode) {
+        return exitCode;
+    }
+
+    if (fallbackArch) {
+        copyWstr(&env->architecture, fallbackArch);
+    } else {
+        DWORD binaryType;
+        BOOL success = GetBinaryTypeW(env->executablePath, &binaryType);
+        if (!success) {
+            return RC_NO_PYTHON;
+        }
+
+        switch (binaryType) {
+        case SCS_32BIT_BINARY:
+            copyWstr(&env->architecture, L"32bit");
+            break;
+        case SCS_64BIT_BINARY:
+            copyWstr(&env->architecture, L"64bit");
+            break;
+        default:
+            return RC_NO_PYTHON;
+        }
+    }
+
+    if (0 == _compare(env->architecture, -1, L"32bit", -1)) {
+        size_t tagLength = wcslen(env->tag);
+        if (tagLength <= 3 || 0 != _compare(&env->tag[tagLength - 3], 3, L"-32", 3)) {
+            const wchar_t *rawTag = env->tag;
+            wchar_t *realTag = (wchar_t*) malloc(sizeof(wchar_t) * (tagLength + 4));
+            if (!realTag) {
+                return RC_NO_MEMORY;
+            }
+
+            int count = swprintf_s(realTag, tagLength + 4, L"%s-32", env->tag);
+            if (count == -1) {
+                free(realTag);
+                return RC_INTERNAL_ERROR;
+            }
+
+            env->tag = realTag;
+            free((void*)rawTag);
+        }
+    }
+
+    wchar_t buffer[MAXLEN];
+    if (swprintf_s(buffer, MAXLEN, L"Python %s", env->tag)) {
+        copyWstr(&env->displayName, buffer);
+    }
+
+    return 0;
+}
+
+
 int
 _registryReadEnvironment(const SearchInfo *search, HKEY root, EnvironmentInfo *env, const wchar_t *fallbackArch)
 {
@@ -1403,6 +1504,10 @@ _registryReadEnvironment(const SearchInfo *search, HKEY root, EnvironmentInfo *e
         return RC_NO_PYTHON;
     }
 
+    if (_isLegacyVersion(env)) {
+        return _registryReadLegacyEnvironment(search, root, env, fallbackArch);
+    }
+
     // If pythonw.exe requested, check specific value
     if (search->windowed) {
         exitCode = _registryReadString(&env->executablePath, root, L"InstallPath", L"WindowedExecutablePath");
@@ -1425,6 +1530,11 @@ _registryReadEnvironment(const SearchInfo *search, HKEY root, EnvironmentInfo *e
         return exitCode;
     }
 
+    if (!env->executablePath) {
+        debug(L"# %s/%s has no executable path\n", env->company, env->tag);
+        return RC_NO_PYTHON;
+    }
+
     exitCode = _registryReadString(&env->architecture, root, NULL, L"SysArchitecture");
     if (exitCode) {
         return exitCode;
@@ -1435,29 +1545,6 @@ _registryReadEnvironment(const SearchInfo *search, HKEY root, EnvironmentInfo *e
         return exitCode;
     }
 
-    // Only PythonCore entries will infer executablePath from installDir and architecture from the binary
-    if (0 == _compare(env->company, -1, L"PythonCore", -1)) {
-        if (!env->executablePath) {
-            exitCode = _combineWithInstallDir(
-                &env->executablePath,
-                env->installDir,
-                search->executable,
-                search->executableLength
-            );
-            if (exitCode) {
-                return exitCode;
-            }
-        }
-        if (!env->architecture && env->executablePath && fallbackArch) {
-            copyWstr(&env->architecture, fallbackArch);
-        }
-    }
-
-    if (!env->executablePath) {
-        debug(L"# %s/%s has no executable path\n", env->company, env->tag);
-        return RC_NO_PYTHON;
-    }
-
     return 0;
 }
 
@@ -1486,7 +1573,7 @@ _registrySearchTags(const SearchInfo *search, EnvironmentInfo **result, HKEY roo
                 freeEnvironmentInfo(env);
                 exitCode = 0;
             } else if (!exitCode) {
-                exitCode = addEnvironmentInfo(result, env);
+                exitCode = addEnvironmentInfo(result, NULL, env);
                 if (exitCode) {
                     freeEnvironmentInfo(env);
                     if (exitCode == RC_DUPLICATE_ITEM) {
@@ -1574,7 +1661,7 @@ appxSearch(const SearchInfo *search, EnvironmentInfo **result, const wchar_t *pa
         copyWstr(&env->displayName, buffer);
     }
 
-    int exitCode = addEnvironmentInfo(result, env);
+    int exitCode = addEnvironmentInfo(result, NULL, env);
     if (exitCode) {
         freeEnvironmentInfo(env);
         if (exitCode == RC_DUPLICATE_ITEM) {
@@ -1612,7 +1699,7 @@ explicitOverrideSearch(const SearchInfo *search, EnvironmentInfo **result)
     if (exitCode) {
         goto abort;
     }
-    exitCode = addEnvironmentInfo(result, env);
+    exitCode = addEnvironmentInfo(result, NULL, env);
     if (exitCode) {
         goto abort;
     }
@@ -1661,7 +1748,7 @@ virtualenvSearch(const SearchInfo *search, EnvironmentInfo **result)
     if (exitCode) {
         goto abort;
     }
-    exitCode = addEnvironmentInfo(result, env);
+    exitCode = addEnvironmentInfo(result, NULL, env);
     if (exitCode) {
         goto abort;
     }