Make the log callback atomic.

Use a single call to write the entire line to stderr. Avoids mixed lines
with e.g. multi-component runs

1 files changed, 9 insertions, 2 deletions

diff --git a/src/maximal_slicing_axi_mg.c b/src/maximal_slicing_axi_mg.c
index a3f8578..39cb1f3 100644
--- a/src/maximal_slicing_axi_mg.c
+++ b/src/maximal_slicing_axi_mg.c
@@ -188,10 +188,17 @@ static void log_callback(const MG2DContext *ctx, int level,
 {
     MSMGContext *ms = ctx->opaque;
     int target_level = ms->log_level;
+    uint8_t buf[1024];
+    int ret;
+
     if (level > target_level)
         return;
-    fprintf(stderr, "[%d] t=%g ", ctz(ms->gh->cctk_levfac[0]), ms->gh->cctk_time);
-    vfprintf(stderr, fmt, vl);
+
+    ret = snprintf(buf, sizeof(buf), "[%d] t=%g ", ctz(ms->gh->cctk_levfac[0]), ms->gh->cctk_time);
+    if (ret >= sizeof(buf))
+        return;
+    vsnprintf(buf + ret, sizeof(buf) - ret, fmt, vl);
+    fputs(buf, stderr);
 }
 
 static MG2DContext *solver_alloc(MSMGContext *ms, int level,