From ebfa660b8297170fb0742ac8959aa64940292853 Mon Sep 17 00:00:00 2001
From: Yann Collet <cyan@fb.com>
Date: Fri, 21 Feb 2025 11:36:30 -0800
Subject: [PATCH] introduce ZSTD_USE_C90_QSORT

---
 .github/workflows/dev-short-tests.yml |  2 +-
 lib/dictBuilder/cover.c               | 15 ++++++++-------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/.github/workflows/dev-short-tests.yml b/.github/workflows/dev-short-tests.yml
index 56a46a744..56401db0a 100644
--- a/.github/workflows/dev-short-tests.yml
+++ b/.github/workflows/dev-short-tests.yml
@@ -693,7 +693,7 @@ jobs:
           sudo apt install -y musl-tools
       - name: Compile the project with musl-gcc
         run: |
-          CC=musl-gcc make -j V=1 zstd
+          CC=musl-gcc CPPFLAGS=-DZSTD_USE_C90_QSORT make -j V=1 zstd
 
   intel-cet-compatibility:
     runs-on: ubuntu-latest
diff --git a/lib/dictBuilder/cover.c b/lib/dictBuilder/cover.c
index 2ef33c73e..29820d7e1 100644
--- a/lib/dictBuilder/cover.c
+++ b/lib/dictBuilder/cover.c
@@ -24,9 +24,9 @@
 /* qsort_r is an extension. */
 #if defined(__linux) || defined(__linux__) || defined(linux) || defined(__gnu_linux__) || \
     defined(__CYGWIN__) || defined(__MSYS__)
-#if !defined(_GNU_SOURCE) && !defined(__ANDROID__) /* NDK doesn't ship qsort_r(). */
-#define _GNU_SOURCE
-#endif
+# if !defined(_GNU_SOURCE) && !defined(__ANDROID__) /* NDK doesn't ship qsort_r(). */
+#   define _GNU_SOURCE
+# endif
 #endif
 
 #include <stdio.h>  /* fprintf */
@@ -241,8 +241,9 @@ typedef struct {
   unsigned d;
 } COVER_ctx_t;
 
-#if !defined(_GNU_SOURCE) && !defined(__APPLE__) && !defined(_MSC_VER)
-/* C90 only offers qsort() that needs a global context. */
+#if defined(ZSTD_USE_C90_QSORT) \
+  || (!defined(_GNU_SOURCE) && !defined(__APPLE__) && !defined(_MSC_VER))
+/* Use global context for non-reentrant sort functions */
 static COVER_ctx_t *g_coverCtx = NULL;
 #endif
 
@@ -328,7 +329,7 @@ static void stableSort(COVER_ctx_t *ctx) {
     qsort_r(ctx->suffix, ctx->suffixSize, sizeof(U32),
             ctx,
             (ctx->d <= 8 ? &COVER_strict_cmp8 : &COVER_strict_cmp));
-#elif defined(_GNU_SOURCE)
+#elif defined(_GNU_SOURCE) && !defined(ZSTD_USE_C90_QSORT)
     qsort_r(ctx->suffix, ctx->suffixSize, sizeof(U32),
             (ctx->d <= 8 ? &COVER_strict_cmp8 : &COVER_strict_cmp),
             ctx);
@@ -342,7 +343,7 @@ static void stableSort(COVER_ctx_t *ctx) {
           (ctx->d <= 8 ? &COVER_strict_cmp8 : &COVER_strict_cmp));
 #else /* C90 fallback.*/
     g_coverCtx = ctx;
-    /* TODO(cavalcanti): implement a reentrant qsort() when is not available. */
+    /* TODO(cavalcanti): implement a reentrant qsort() when _r is not available. */
     qsort(ctx->suffix, ctx->suffixSize, sizeof(U32),
           (ctx->d <= 8 ? &COVER_strict_cmp8 : &COVER_strict_cmp));
 #endif