[clang] 3be48a6 - [clang] Fix preprocessor output from #embed (#126742)

[via cfe-commits]

Author: Mariya Podchishchaeva
Date: 2025-02-13T10:59:21+01:00
New Revision: 3be48a6f809afccc9bcddc8cf94492812b49e1f7

URL: https://github.com/llvm/llvm-project/commit/3be48a6f809afccc9bcddc8cf94492812b49e1f7
DIFF: https://github.com/llvm/llvm-project/commit/3be48a6f809afccc9bcddc8cf94492812b49e1f7.diff

LOG: [clang] Fix preprocessor output from #embed (#126742)

When bytes with negative signed char values appear in the data, make
sure to use raw bytes from the data string when preprocessing, not char
values.

Fixes https://github.com/llvm/llvm-project/issues/102798

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/Frontend/PrintPreprocessedOutput.cpp
    clang/test/Preprocessor/embed_preprocess_to_file.c

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index b4e0762dcca1c..afd5cdc9c49e1 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -147,6 +147,9 @@ Improvements to Coverage Mapping
 Bug Fixes in This Version
 -------------------------
 
+- Clang now outputs correct values when #embed data contains bytes with negative
+  signed char values (#GH102798).
+
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

diff  --git a/clang/lib/Frontend/PrintPreprocessedOutput.cpp b/clang/lib/Frontend/PrintPreprocessedOutput.cpp
index 1005825441b3e..2ae355fb33885 100644
--- a/clang/lib/Frontend/PrintPreprocessedOutput.cpp
+++ b/clang/lib/Frontend/PrintPreprocessedOutput.cpp
@@ -974,11 +974,10 @@ static void PrintPreprocessedTokens(Preprocessor &PP, Token &Tok,
       // Loop over the contents and print them as a comma-delimited list of
       // values.
       bool PrintComma = false;
-      for (auto Iter = Data->BinaryData.begin(), End = Data->BinaryData.end();
-           Iter != End; ++Iter) {
+      for (unsigned char Byte : Data->BinaryData.bytes()) {
         if (PrintComma)
           *Callbacks->OS << ", ";
-        *Callbacks->OS << static_cast<unsigned>(*Iter);
+        *Callbacks->OS << static_cast<int>(Byte);
         PrintComma = true;
       }
     } else if (Tok.isAnnotation()) {

diff  --git a/clang/test/Preprocessor/embed_preprocess_to_file.c b/clang/test/Preprocessor/embed_preprocess_to_file.c
index 9895d958cf96d..b3c99d36f784a 100644
--- a/clang/test/Preprocessor/embed_preprocess_to_file.c
+++ b/clang/test/Preprocessor/embed_preprocess_to_file.c
@@ -37,3 +37,11 @@ const char even_more[] = {
 // DIRECTIVE-NEXT: #embed <jk.txt> prefix(4, 5,) suffix(, 6, 7) /* clang -E -dE */
 // DIRECTIVE-NEXT:  , 8, 9, 10
 // DIRECTIVE-NEXT: };
+
+constexpr char big_one[] = {
+#embed <big_char.txt>
+};
+
+// EXPANDED: constexpr char big_one[] = {255
+// DIRECTIVE: constexpr char big_one[] = {
+// DIRECTIVE-NEXT: #embed <big_char.txt>