Merge pull request cc65#2112 from bbbradsmith/extern-static-conflict-…

…error Error/warning for extern/static linkage declaration conflict
karrika · May 12, 2023 · 55723f4 · 55723f4
2 parents 79018fd + 5a30d74
commit 55723f4
Show file tree

Hide file tree

Showing 2 changed files with 12 additions and 10 deletions.
diff --git a/src/cc65/symtab.c b/src/cc65/symtab.c
@@ -1340,15 +1340,14 @@ SymEntry* AddGlobalSym (const char* Name, const Type* T, unsigned Flags)
                    Name);
             Entry = 0;
         } else if ((Flags & SC_ESUTYPEMASK) != SC_TYPEDEF) {
-            /* If a static declaration follows a non-static declaration, then
-            ** diagnose the conflict. It will warn and compile an extern
-            ** declaration if both declarations are global, otherwise give an
-            ** error.
+            /* If a static declaration follows a non-static declaration, then the result is undefined.
+            ** Most compilers choose to either give an error at compile time,
+            ** or remove the extern property for a link time error if used.
             */
             if (SymTab == SymTab0           &&
                 (Flags & SC_EXTERN) == 0    &&
                 (Entry->Flags & SC_EXTERN) != 0) {
-                Warning ("Static declaration of '%s' follows non-static declaration", Name);
+                Error ("Static declaration of '%s' follows non-static declaration", Name);
             } else if ((Flags & SC_EXTERN) != 0                                     &&
                        (Entry->Owner == SymTab0 || (Entry->Flags & SC_DEF) != 0)    &&
                        (Entry->Flags & SC_EXTERN) == 0) {
@@ -1360,8 +1359,12 @@ SymEntry* AddGlobalSym (const char* Name, const Type* T, unsigned Flags)
                 */
                 if (Entry->Owner == SymTab0) {
                     if ((Flags & SC_STORAGE) == 0) {
-                        /* Linkage must be unchanged */
+                        /* Linkage must be unchanged.
+                        ** The C standard specifies that a later extern declaration will be ignored,
+                        ** and will use the previous linkage instead. Giving a warning for this case.
+                        */
                         Flags &= ~SC_EXTERN;
+                        Warning ("Extern declaration of '%s' follows static declaration, extern ignored", Name);
                     } else {
                         Error ("Non-static declaration of '%s' follows static declaration", Name);
                     }

diff --git a/test/val/decl-static-extern.c b/test/val/decl-static-extern.c
@@ -7,13 +7,12 @@
 
 /*
   see: https://github.com/cc65/cc65/issues/191
+       https://github.com/cc65/cc65/issues/2111
 */
 
-#pragma warn(error, on)
-
 static int n = 0;
-extern int n;           /* should not give an error */
-static int n;           /* should not give an error */
+extern int n;           /* extern is ignored, gives a warning but keeps previous static definiton */
+static int n;           /* no error or warning, the previous static is still in effect */
 
 int main(void)
 {