gout

commit f1c0362fd86ca639e2694d1343afce39d39a80d6
parent 2ed590a4100e6c6ecb4ae72dbed322774f85baf0
Author: Chris Bracken <chris@bracken.jp>
Date:   Sat,  6 Jun 2026 14:42:23 +0900

fs_inmemory: prevent duplicate file slots and stale reads

When opening a file in write mode, reuse the existing file slot if the
path already exists instead of appending a duplicate slot in order to
prevent readers in read mode from reading stale content from the first
slot.

Diffstat:
M
src/fs_inmemory.c
 | 
25
++++++++++++++++++-------
M
src/gout_tests.c
 | 
37
+++++++++++++++++++++++++++++++++++++

2 files changed, 55 insertions(+), 7 deletions(-)
diff --git a/src/fs_inmemory.c b/src/fs_inmemory.c
@@ -43,14 +43,25 @@ static int inmemory_mkdirp(const char* path) {
 
 static FILE* inmemory_fopen(const char* path, const char* mode) {
   if (strcmp(mode, "w") == 0) {
-    if (g_files_count >= MAX_MOCK_FILES) {
-      return NULL;
+    InMemoryFile* file = NULL;
+    for (size_t i = 0; i < g_files_count; i++) {
+      if (strcmp(g_files[i].path, path) == 0) {
+        file = &g_files[i];
+        free(file->buf);
+        file->buf = NULL;
+        file->size = 0;
+        break;
+      }
+    }
+    if (!file) {
+      if (g_files_count >= MAX_MOCK_FILES) {
+        return NULL;
+      }
+      file = &g_files[g_files_count++];
+      file->path = estrdup(path);
+      file->buf = NULL;
+      file->size = 0;
     }
-    // Register a new file.
-    InMemoryFile* file = &g_files[g_files_count++];
-    file->path = estrdup(path);
-    file->buf = NULL;
-    file->size = 0;
     FILE* f = open_memstream(&file->buf, &file->size);
     register_active_stream(f);
     return f;
diff --git a/src/gout_tests.c b/src/gout_tests.c
@@ -16,3 +16,40 @@ UTEST(gout_options_create, ReturnsInitializedOptions) {
   ASSERT_NE(NULL, options);
   gout_options_free(options);
 }
+
+#include "fs_inmemory.h"
+
+UTEST(fs_inmemory, overwrite_file) {
+  inmemory_fs_clear();
+
+  // 1. Write initial content.
+  FILE* f1 = g_fs_inmemory->fopen("test_file.txt", "w");
+  ASSERT_NE(NULL, f1);
+  fprintf(f1, "Initial Content");
+  g_fs_inmemory->fclose(f1);
+
+  // Verify we can read it.
+  FILE* r1 = g_fs_inmemory->fopen("test_file.txt", "r");
+  ASSERT_NE(NULL, r1);
+  char buf[64];
+  memset(buf, 0, sizeof(buf));
+  fgets(buf, sizeof(buf), r1);
+  EXPECT_STREQ("Initial Content", buf);
+  g_fs_inmemory->fclose(r1);
+
+  // 2. Overwrite the file.
+  FILE* f2 = g_fs_inmemory->fopen("test_file.txt", "w");
+  ASSERT_NE(NULL, f2);
+  fprintf(f2, "New Updated Content");
+  g_fs_inmemory->fclose(f2);
+
+  // Verify that the read returns the NEW updated content.
+  FILE* r2 = g_fs_inmemory->fopen("test_file.txt", "r");
+  ASSERT_NE(NULL, r2);
+  memset(buf, 0, sizeof(buf));
+  fgets(buf, sizeof(buf), r2);
+  EXPECT_STREQ("New Updated Content", buf);
+  g_fs_inmemory->fclose(r2);
+
+  inmemory_fs_clear();
+}